跳转到内容
打开/关闭菜单
  • 451 条目
  • 806 文件
  • 22 用户
  • 9187 编辑
Blockland Wiki
打开/关闭外观设置菜单
打开/关闭个人菜单
未登录
未登录用户的IP地址会在进行任意编辑后公开展示。

MediaWiki:KuranokaPageTransition.js:修订间差异

MediaWiki界面页面
无编辑摘要
无编辑摘要
第1行: 第1行:
/* ============================================================
/* ============================================================
   Kuranoka / Kuronata — Page Transition V30 / WebGL2
   Kuranoka / Kuronata — Page Transition V31 / WebGL2
   V25 motion and V13/P3's oppressive, wide white-hot fire wall.
   V25 motion and V13/P3's oppressive, wide white-hot fire wall.
   The BODY of the fire, not just the glowing edge, is rendered by GPU.
   The BODY of the fire, not just the glowing edge, is rendered by GPU.
第62行: 第62行:
         if(!document.head || document.getElementById('kkpt-css-retry'))return;
         if(!document.head || document.getElementById('kkpt-css-retry'))return;
         try{
         try{
             if(getComputedStyle(root).getPropertyValue('--kkpt-css-v30').trim()==='ready')
             if(getComputedStyle(root).getPropertyValue('--kkpt-css-v31').trim()==='ready')
                 return;
                 return;
         }catch(_){}
         }catch(_){}
第72行: 第72行:
         target.searchParams.set('action','raw');
         target.searchParams.set('action','raw');
         target.searchParams.set('ctype','text/css');
         target.searchParams.set('ctype','text/css');
         target.searchParams.set('kkptv','30');
         target.searchParams.set('kkptv','31');
         link.href=target.href;
         link.href=target.href;
         link.addEventListener('error',()=>console.warn(
         link.addEventListener('error',()=>console.warn(
第323行: 第323行:
     if (window!==window.top || window.__kkptV12) return;
     if (window!==window.top || window.__kkptV12) return;
     window.__kkptV12=true;
     window.__kkptV12=true;
     window.__kkptVersion='30.0';
     window.__kkptVersion='31.0';


     // Easter eggs + Infobox gear are the default. No floating pill.
     // Easter eggs + Infobox gear are the default. No floating pill.
第982行: 第982行:
                     const r=Math.random();
                     const r=Math.random();
                     const kind=dark
                     const kind=dark
                         ? r<.55?'flame':r<.90?'ember':'ash'
                         ? r<.36?'flame':r<.89?'ember':'ash'
                         : r<.37?'glow':r<.81?'leaf':'pollen';
                         : r<.37?'glow':r<.81?'leaf':'pollen';
                     const small=kind==='ember'||kind==='pollen';
                     const small=kind==='ember'||kind==='pollen';
                     const soot=kind==='ash';
                     const soot=kind==='ash';
                     const life=dark
                     const life=dark
                         ? (soot?.7+Math.random()*1.1:
                         ? (soot?.7+Math.random()*1.4:
                             small?.65+Math.random()*1.1:.42+Math.random()*.76)
                             small?1.05+Math.random()*1.75:.42+Math.random()*.76)
                         : 1.15+Math.random()*1.55;
                         : 1.15+Math.random()*1.55;
                     combustion.push({
                     combustion.push({
                         kind,x:edge+(dark?1:-1)*(Math.random()*47-8),
                         kind,x:edge+(dark?1:-1)*(Math.random()*47-8),
                         y:y+(Math.random()-.5)*25,
                         y:y+(Math.random()-.5)*25,
                         vx:(dark?1:-1)*(dark?14+Math.random()*154:
                         vx:(dark?1:-1)*(dark?(small?85+Math.random()*320:
                            14+Math.random()*154):
                             16+Math.random()*69),
                             16+Math.random()*69),
                         vy:-(dark?32+Math.random()*171:12+Math.random()*57),
                         vy:-(dark?(small?12+Math.random()*205:
                            32+Math.random()*171):12+Math.random()*57),
                         life,remaining:life,
                         life,remaining:life,
                         radius:dark
                         radius:dark
                             ? (soot?1.2+Math.random()*2.7:
                             ? (soot?1.2+Math.random()*2.7:
                                 small?2+Math.random()*5:9+Math.random()*19)
                                 small?2+Math.random()*4.8:9+Math.random()*19)
                             : kind==='glow'?26+Math.random()*49:
                             : kind==='glow'?26+Math.random()*49:
                                 kind==='leaf'?4+Math.random()*6:
                                 kind==='leaf'?4+Math.random()*6:
第1,029行: 第1,031行:
                     // Charcoal sheets tear off in irregular polygons, not
                     // Charcoal sheets tear off in irregular polygons, not
                     // squares or narrow glitch streaks.
                     // squares or narrow glitch streaks.
                     shardRemainder+=dt*(h<680?9:15);
                     shardRemainder+=dt*(h<680?41:69);
                     const shardBirths=Math.min(5,Math.floor(shardRemainder));
                     const shardBirths=Math.min(13,Math.floor(shardRemainder));
                     shardRemainder-=shardBirths;
                     shardRemainder-=shardBirths;
                     for(let i=0;i<shardBirths&&tornPaper.length<135;i++){
                     for(let i=0;i<shardBirths&&tornPaper.length<330;i++){
                         const y=Math.random()*h;
                         const y=Math.random()*h;
                         const life=.82+Math.random()*1.55;
                         const life=1.00+Math.random()*2.05;
                         const points=6+Math.floor(Math.random()*4);
                         const points=8+Math.floor(Math.random()*8);
                         const outline=Array.from({length:points},(_,j)=>({
                         const outline=Array.from({length:points},(_,j)=>({
                             a:Math.PI*2*j/points+(Math.random()-.5)*.22,
                             a:Math.PI*2*j/points+(Math.random()-.5)*.52,
                             r:.50+Math.random()*.61
                             r:.20+Math.random()*1.16
                         }));
                         }));
                         tornPaper.push({
                         tornPaper.push({
                             x:edgeAt(y,seconds,progress,w)+(Math.random()-.5)*47,
                             x:edgeAt(y,seconds,progress,w)+(Math.random()-.2)*66,
                             y, vx:34+Math.random()*210,
                             y, vx:58+Math.random()*330,
                             vy:-170+Math.random()*260,
                             vy:-210+Math.random()*295,
                             gravity:90+Math.random()*150,
                             gravity:90+Math.random()*150,
                             radius:3+Math.pow(Math.random(),1.6)*15,
                             radius:2+Math.pow(Math.random(),2.7)*23,
                             angle:Math.random()*6.28,
                             angle:Math.random()*6.28,
                             spin:(Math.random()-.5)*7,
                             spin:(Math.random()-.5)*7,
第1,088行: 第1,090行:
             bend:rand(i*15+23)*6.28
             bend:rand(i*15+23)*6.28
         }));
         }));
         const motes=Array.from({length:innerWidth<700?37:72},(_,i)=>({
         const motes=Array.from({length:innerWidth<700?92:175},(_,i)=>({
             y:rand(i*3+17),phase:rand(i*9+43),
             y:rand(i*3+17),phase:rand(i*9+43),
             speed:85+rand(i*12+5)*260,
             speed:105+rand(i*12+5)*410,
             drift:75+rand(i*15+2)*170,
             drift:90+rand(i*15+2)*460,
             length:3+rand(i*17+7)*11
             length:5+rand(i*17+7)*26
         }));
         }));
         const shockDebris=Array.from({length:innerWidth<700?40:85},(_,i)=>({
         const shockDebris=Array.from({length:innerWidth<700?40:85},(_,i)=>({
第1,134行: 第1,136行:
             ctx.globalAlpha=.72*fade;
             ctx.globalAlpha=.72*fade;
             ctx.shadowColor='#ff2903';
             ctx.shadowColor='#ff2903';
             ctx.shadowBlur=30;
             ctx.shadowBlur=18;
             ctx.strokeStyle='#ff3008';
             ctx.strokeStyle='#ff3008';
             ctx.lineWidth=40;
             ctx.lineWidth=19;
             ctx.stroke();
             ctx.stroke();
             ctx.globalAlpha=.83*fade;
             ctx.globalAlpha=.83*fade;
             ctx.shadowColor='#ffa620';
             ctx.shadowColor='#ffa620';
             ctx.shadowBlur=19;
             ctx.shadowBlur=12;
             ctx.strokeStyle='#ff9c12';
             ctx.strokeStyle='#ff9c12';
             ctx.lineWidth=20;
             ctx.lineWidth=9;
             ctx.stroke();
             ctx.stroke();
             ctx.globalAlpha=.89*fade;
             ctx.globalAlpha=.89*fade;
第1,148行: 第1,150行:
             ctx.shadowBlur=8;
             ctx.shadowBlur=8;
             ctx.strokeStyle='#ffdf54';
             ctx.strokeStyle='#ffdf54';
             ctx.lineWidth=9;
             ctx.lineWidth=5;
             ctx.stroke();
             ctx.stroke();
             ctx.globalAlpha=.93*fade;
             ctx.globalAlpha=.93*fade;
第1,154行: 第1,156行:
             ctx.shadowBlur=4;
             ctx.shadowBlur=4;
             ctx.strokeStyle='#fffce8';
             ctx.strokeStyle='#fffce8';
             ctx.lineWidth=3.2;
             ctx.lineWidth=1.9;
             ctx.stroke();
             ctx.stroke();
             ctx.shadowBlur=0;
             ctx.shadowBlur=0;
第1,493行: 第1,495行:
                 const opacity=clamp01(p.remaining/.22)*
                 const opacity=clamp01(p.remaining/.22)*
                     clamp01(age/.08)*(1-age*.30)*
                     clamp01(age/.08)*(1-age*.30)*
                     (p.kind==='ember'?.74:p.kind==='glow'?.13:.66)*fade*
                     (p.kind==='ember'?.93:p.kind==='glow'?.13:.62)*fade*
                     (dark?Math.exp(-Math.max(0,p.x-
                     (dark?Math.exp(-Math.max(0,p.x-
                         edgeAt(p.y,seconds,progress,w))/70):1);
                         edgeAt(p.y,seconds,progress,w))/
                        (p.kind==='ember'?475:145)):1);
                 if(opacity<.012)continue;
                 if(opacity<.012)continue;
                 ctx.save();
                 ctx.save();
第1,586行: 第1,589行:
                     });
                     });
                     ctx.closePath();
                     ctx.closePath();
                    // Distinct silhouette first: some fragments are almost
                    // pitch black against the blazing furnace.
                     ctx.shadowBlur=7;
                     ctx.shadowBlur=7;
                     ctx.shadowColor='#090506';
                     ctx.shadowColor=age<.40?'#ff5d1b':'#0b0407';
                     ctx.fillStyle=p.seed>3?'#190d11':'#302025';
                     ctx.fillStyle=p.seed>3?'#080408':'#241014';
                     ctx.fill();
                     ctx.fill();
                     ctx.shadowBlur=0;
                     ctx.shadowBlur=0;
                     ctx.lineWidth=.8+Math.sin(p.seed)**2*.8;
                    // Only discontinuous edges glow: a complete neon
                     ctx.strokeStyle=age<.48?'rgba(255,98,34,.29)':
                    // polygon outline looks like a sci-fi icon, not char.
                         'rgba(49,20,19,.47)';
                     ctx.lineWidth=.70+Math.sin(p.seed)**2*.95;
                     ctx.strokeStyle=age<.50?'rgba(255,112,34,.82)':
                         'rgba(125,32,16,.31)';
                    ctx.beginPath();
                    for(let i=0;i<p.outline.length;i++){
                        if((i+Math.floor(p.seed*7))%4>1)continue;
                        const a=p.outline[i];
                        const b=p.outline[(i+1)%p.outline.length];
                        ctx.moveTo(Math.cos(a.a)*a.r*p.radius,
                            Math.sin(a.a)*a.r*p.radius*.74);
                        ctx.lineTo(Math.cos(b.a)*b.r*p.radius,
                            Math.sin(b.a)*b.r*p.radius*.74);
                    }
                     ctx.stroke();
                     ctx.stroke();
                    // Cracks are molten for the first half of the flight.
                    if(age<.55){
                        ctx.globalCompositeOperation='lighter';
                        ctx.shadowBlur=6;
                        ctx.shadowColor='#ff5e0a';
                        ctx.strokeStyle=age<.22?'#ffe9a2':'#ff761e';
                        ctx.lineWidth=.60+(.55-age)*1.4;
                        ctx.globalAlpha=opacity*(1-age);
                        ctx.beginPath();
                        ctx.moveTo(-p.radius*.48,-p.radius*.06);
                        ctx.lineTo(-p.radius*.08,p.radius*.14);
                        ctx.lineTo(p.radius*.27,-p.radius*.22);
                        ctx.stroke();
                        ctx.shadowBlur=0;
                        ctx.globalCompositeOperation='source-over';
                        ctx.globalAlpha=opacity;
                    }
                     // Thin blue-white unburnt fibers still visible on a
                     // Thin blue-white unburnt fibers still visible on a
                     // few ripped faces, before the back chars completely.
                     // few ripped faces, before the back chars completely.
第1,617行: 第1,651行:
                 const x=edgeAt(yy,seconds,progress,w)+direction*age*mote.drift;
                 const x=edgeAt(yy,seconds,progress,w)+direction*age*mote.drift;
                 if(x<-25||x>w+25||yy<-25||yy>h+25)continue;
                 if(x<-25||x>w+25||yy<-25||yy>h+25)continue;
                 const opacity=(1-age)*fade*.89;
                 const opacity=(1-age)*fade*.98;
                 ctx.globalAlpha=opacity;
                 ctx.globalAlpha=opacity;
                 ctx.strokeStyle='#ffb45d';
                ctx.shadowColor='#ff8c28';
                 ctx.lineWidth=.8;
                ctx.shadowBlur=5;
                 ctx.strokeStyle=age<.37?'#fff2a1':'#ff922d';
                 ctx.lineWidth=1.0+(.5-age)*.7;
                 ctx.beginPath();
                 ctx.beginPath();
                 ctx.moveTo(x,yy);
                 ctx.moveTo(x,yy);
第1,626行: 第1,662行:
                 ctx.stroke();
                 ctx.stroke();
             }
             }
            ctx.shadowBlur=0;
             ctx.restore();}
             ctx.restore();}
         };
         };
第1,696行: 第1,733行:
             :-105+(w+210)*smooth(t);
             :-105+(w+210)*smooth(t);
         return y=>center+wave*(
         return y=>center+wave*(
             13*Math.sin(y*.023+seconds*5.5)+
             10*Math.sin(y*.023+seconds*5.5)+
             7*Math.sin(y*.071-seconds*8.4)+
             5*Math.sin(y*.071-seconds*8.4)+
             4*Math.sin(y*.14+seconds*12)+
             3*Math.sin(y*.14+seconds*12)+
             20*edgeShard(y/32+seconds*.48,1.73)+
             12*edgeShard(y/32+seconds*.48,1.73)+
             8*edgeShard(y/10-seconds*1.2,4.19));
             6*edgeShard(y/10-seconds*1.2,4.19));
     }
     }


第1,772行: 第1,809行:
                 float wobble=sin(3.14159265*t);
                 float wobble=sin(3.14159265*t);
                 return center+wobble*(
                 return center+wobble*(
                     13.0*sin(y*.023+clock*5.5)+
                     10.0*sin(y*.023+clock*5.5)+
                     7.0*sin(y*.071-clock*8.4)+
                     5.0*sin(y*.071-clock*8.4)+
                     4.0*sin(y*.14+clock*12.0)+
                     3.0*sin(y*.14+clock*12.0)+
                     20.0*angular(y/32.0+clock*.48,1.73)+
                     12.0*angular(y/32.0+clock*.48,1.73)+
                     8.0*angular(y/10.0-clock*1.2,4.19));
                     6.0*angular(y/10.0-clock*1.2,4.19));
             }
             }
         `;
         `;
第2,004行: 第2,041行:
                     ?uView.x+105.0-(uView.x+210.0)*sm(uProgress)
                     ?uView.x+105.0-(uView.x+210.0)*sm(uProgress)
                     :-105.0+(uView.x+210.0)*sm(uProgress);
                     :-105.0+(uView.x+210.0)*sm(uProgress);
                 return c+wave*(13.0*sin(y*.023+uClock*5.5)+
                 return c+wave*(10.0*sin(y*.023+uClock*5.5)+
                     7.0*sin(y*.071-uClock*8.4)+
                     5.0*sin(y*.071-uClock*8.4)+
                     4.0*sin(y*.14+uClock*12.0)+
                     3.0*sin(y*.14+uClock*12.0)+
                     20.0*angular(y/32.0+uClock*.48,1.73)+
                     12.0*angular(y/32.0+uClock*.48,1.73)+
                     8.0*angular(y/10.0-uClock*1.2,4.19));
                     6.0*angular(y/10.0-uClock*1.2,4.19));
             }
             }


第2,035行: 第2,072行:
                 }
                 }


                 float span=clamp(uView.x*.29,205.0,550.0);
                 float span=clamp(uView.x*.225,175.0,475.0);
                 if(d < -75.0 || d > span+800.0){
                 if(d < -75.0 || d > span+800.0){
                     outColor=vec4(0.0);return;
                     outColor=vec4(0.0);return;
第2,153行: 第2,190行:
                 col=mix(col,vec3(1.0,.19,.003),luminous*.92);
                 col=mix(col,vec3(1.0,.19,.003),luminous*.92);
                 col=mix(col,vec3(1.0,.70,.035),
                 col=mix(col,vec3(1.0,.70,.035),
                     clamp(body*yellow*.86,0.0,1.0));
                     clamp(body*yellow*.72,0.0,1.0));
                 col=mix(col,vec3(1.0,.23,.006),
                 col=mix(col,vec3(1.0,.23,.006),
                     clamp(cellGlow*.90*lip,0.0,1.0));
                     clamp(cellGlow*.90*lip,0.0,1.0));
第2,159行: 第2,196行:
                     clamp(cellGold*.98*lip,0.0,1.0));
                     clamp(cellGold*.98*lip,0.0,1.0));
                 col=mix(col,vec3(1.0,.99,.82),
                 col=mix(col,vec3(1.0,.99,.82),
                     clamp(hot*.25+cellWhite*1.25*lip+
                     clamp(hot*.15+cellWhite*1.01*lip+
                         whiteRim*.96,0.0,1.0));
                         whiteRim*.86,0.0,1.0));
                 col+=vec3(.15,.034,.0)*near;
                 col+=vec3(.15,.034,.0)*near;


                 float alpha=clamp(shroud*.23*(1.0-body*.83)*burnMask+
                 float alpha=clamp(shroud*.27*(1.0-body*.83)*burnMask+
                     body*1.05*burnMask+cellGlow*.96*lip+
                     body*.91*burnMask+cellGlow*.86*lip+
                     near*.68+whiteRim*.32,0.0,.99);
                     near*.68+whiteRim*.32,0.0,.99);
                 // Remove flat horizontal slabs leaking into the old sky.
                 // Remove flat horizontal slabs leaking into the old sky.
第2,274行: 第2,311行:
                     (uView.y+220.0)+80.0-
                     (uView.y+220.0)+80.0-
                     phase*(145.0+150.0*seed);
                     phase*(145.0+150.0*seed);
                 float span=clamp(uView.x*.29,205.0,550.0);
                 float span=clamp(uView.x*.225,175.0,475.0);
                 float trail=19.0+pow(hash(vec2(id*2.17,5.3)),.75)*
                 float trail=19.0+pow(hash(vec2(id*2.17,5.3)),.75)*
                     span*.88;
                     span*.88;
第2,281行: 第2,318行:
                     sin(uClock*2.9+seed*6.283+phase*5.0)*
                     sin(uClock*2.9+seed*6.283+phase*5.0)*
                     (7.0+12.0*phase);
                     (7.0+12.0*phase);
                 float width=(17.0+57.0*hash(vec2(id*1.93,7.2)))*
                 float width=(14.0+50.0*hash(vec2(id*1.93,7.2)))*
                     (.75+.30*sin(phase*3.14159));
                     (.75+.30*sin(phase*3.14159));
                 float height=(57.0+131.0*hash(vec2(id*.89,11.1)))*
                 float height=(57.0+131.0*hash(vec2(id*.89,11.1)))*
第2,350行: 第2,387行:
                     clamp(gold*.43+white*.55,0.0,1.0));
                     clamp(gold*.43+white*.55,0.0,1.0));
                 col=mix(col,vec3(1.0,.998,.86),
                 col=mix(col,vec3(1.0,.998,.86),
                     clamp(white*.97,0.0,1.0));
                     clamp(white*.80,0.0,1.0));
                 float a=plume*vHeat*(.20+.25*flux)+
                 float a=plume*vHeat*(.15+.15*flux)+
                     white*vHeat*.12;
                     white*vHeat*.10;
                 outColor=vec4(col,clamp(a,0.0,.70));
                 outColor=vec4(col,clamp(a,0.0,.56));
             }`;
             }`;


第2,425行: 第2,462行:
                 if(dark){
                 if(dark){
                     gl.enable(gl.BLEND);
                     gl.enable(gl.BLEND);
                    // Charcoal dust is physically in FRONT of burning
                    // paper but BELOW the incandescent plume layer.
                    setUniforms(sparks,clock,progress,phase,tail,scale);
                    if(sparks.locations.uRenderMode)
                        gl.uniform1f(sparks.locations.uRenderMode,0);
                    gl.blendFuncSeparate(gl.SRC_ALPHA,
                        gl.ONE_MINUS_SRC_ALPHA,gl.ONE,
                        gl.ONE_MINUS_SRC_ALPHA);
                    gl.drawArrays(gl.POINTS,0,mobile?750:1700);
                     gl.blendFuncSeparate(gl.SRC_ALPHA,gl.ONE,
                     gl.blendFuncSeparate(gl.SRC_ALPHA,gl.ONE,
                         gl.ONE,gl.ONE_MINUS_SRC_ALPHA);
                         gl.ONE,gl.ONE_MINUS_SRC_ALPHA);
                     setUniforms(plumes,clock,progress,phase,tail,scale);
                     setUniforms(plumes,clock,progress,phase,tail,scale);
                     const flameCount=Math.round((view[1]/360)*
                     const flameCount=Math.round((view[1]/360)*
                         (mobile?65:85)*Math.min(1.45,view[0]/640));
                         (mobile?42:51)*Math.min(1.45,view[0]/640));
                     gl.drawArraysInstanced(gl.TRIANGLES,0,6,
                     gl.drawArraysInstanced(gl.TRIANGLES,0,6,
                         Math.max(45,Math.min(flameCount,mobile?210:390)));
                         Math.max(20,Math.min(flameCount,mobile?115:210)));
 
                    // Actual WebGL2 cinders above the flames, in addition
                    // to V25's longer 2D particle streaks.
                    setUniforms(sparks,clock,progress,phase,tail,scale);
                    if(sparks.locations.uRenderMode)
                        gl.uniform1f(sparks.locations.uRenderMode,1);
                    gl.drawArrays(gl.POINTS,0,mobile?1500:3300);
                     gl.disable(gl.BLEND);
                     gl.disable(gl.BLEND);
                 }
                 }
第2,474行: 第2,528行:
             if(!gl){surface.remove();return null;}
             if(!gl){surface.remove();return null;}
             curtain=program(backgroundVert,dominantFireFrag);
             curtain=program(backgroundVert,dominantFireFrag);
             if(dark)plumes=program(plumeVert,plumeFrag);
             if(dark){
                plumes=program(plumeVert,plumeFrag);
                sparks=program(sparkVert,sparkFrag);
            }
             // No abstract, additive GPU spark pass: P3's fire requires
             // No abstract, additive GPU spark pass: P3's fire requires
             // textured smoke and incandescent streaks, not neon points.
             // textured smoke and incandescent streaks, not neon points.

2026年10月24日 (六) 12:00的版本

/* ============================================================
   Kuranoka / Kuronata — Page Transition V31 / WebGL2
   V25 motion and V13/P3's oppressive, wide white-hot fire wall.
   The BODY of the fire, not just the glowing edge, is rendered by GPU.
   Detailed embers, soot and storm debris preserve V13's atmosphere.
   Canvas 2D engine retained as the no-WebGL fallback.
   Only this page-scoped JS/CSS; never modify Citizen or loader.js.
   Real page navigation after the transition; iframe is visual-only.
   ============================================================ */
(function initKkpt(retry) {
    'use strict';
    retry=retry||0;
    // A separately imported page script may arrive before mw.config.
    // Retry rather than silently abandoning the entire world.
    if (!window.mw || !mw.config || typeof mw.config.get!=='function') {
        if(retry<40)setTimeout(()=>initKkpt(retry+1),100);
        return;
    }

    const pathMatch = location.pathname.match(/\/wiki\/(Kuranoka|Kuronata)\/?$/);
    const urlPage = pathMatch ? pathMatch[1]
        : new URLSearchParams(location.search).get('title');
    const basePage = ['Kuranoka','Kuronata'].includes(urlPage)
        ? urlPage : mw.config.get('wgPageName');
    const action = new URLSearchParams(location.search).get('action') || 'view';
    if (!['Kuranoka','Kuronata'].includes(basePage) || action !== 'view') return;

    // V24: the two article worlds have deliberate, deterministic palettes.
    // "os" is NOT a light theme: it can resolve to dark on the reader's
    // computer. Session storage may also be unavailable. Therefore, never
    // restore a stale "os" token when landing back on Kuranoka.
    const root=document.documentElement;
    const themeNames=['skin-theme-clientpref-day','skin-theme-clientpref-os',
        'skin-theme-clientpref-night','skin-theme-clientpref-black',
        'skin-citizen-light'];
    let wantsNight=basePage==='Kuronata';
    let changingTheme=false;
    function syncTheme(){
        if(changingTheme)return;
        const wanted=wantsNight?'skin-theme-clientpref-night':
            'skin-theme-clientpref-day';
        const shadow=wantsNight?'kkpt-kuronata-dark':null;
        const unexpected=themeNames.filter(c=>c!==wanted)
            .concat(wantsNight?[]:['kkpt-kuronata-dark']);
        if(root.classList.contains(wanted)&&
            (!shadow||root.classList.contains(shadow))&&
            unexpected.every(c=>!root.classList.contains(c))){
            return;
        }
        changingTheme=true;
        root.classList.remove(...themeNames,'kkpt-kuronata-dark');
        root.classList.add(wanted);
        if(shadow)root.classList.add(shadow);
        changingTheme=false;
    }
    function showTheme(dark){wantsNight=dark;syncTheme();}
    syncTheme();
    // CSS and JS are sometimes loaded independently on this wiki.
    // A sentinel distinguishes a missing stylesheet from slow image
    // decoding. A single same-origin retry prevents unstyled effects.
    function ensureWorldStyles(){
        if(!document.head || document.getElementById('kkpt-css-retry'))return;
        try{
            if(getComputedStyle(root).getPropertyValue('--kkpt-css-v31').trim()==='ready')
                return;
        }catch(_){}
        const link=document.createElement('link');
        link.id='kkpt-css-retry';
        link.rel='stylesheet';
        const target=new URL('/index.php',location.origin);
        target.searchParams.set('title','MediaWiki:KuranokaPageTransition.css');
        target.searchParams.set('action','raw');
        target.searchParams.set('ctype','text/css');
        target.searchParams.set('kkptv','31');
        link.href=target.href;
        link.addEventListener('error',()=>console.warn(
            '[KuranokaPageTransition] Stylesheet retry failed; '+
            'check ResourceLoader / CSS permissions.'));
        document.head.appendChild(link);
    }
    setTimeout(ensureWorldStyles,1200);
    // Citizen's later initialization may reinstate the OS-preference class.
    // Keep the intended world palette without touching the user's global
    // account preference or other MediaWiki pages.
    new MutationObserver(syncTheme).observe(root,{
        attributes:true,attributeFilter:['class']
    });
    function navigateRealPage(href){
        window.location.assign(href);
    }

    // V17: the dark-world extras run in *both* the visible document and
    // its same-origin preview iframe. They never alter other Wiki pages.
    function installKuronataAfterglow() {
        if(basePage!=='Kuronata'||window.__kkptDarkExtrasReady)return;
        window.__kkptDarkExtrasReady=true;
        const prefersReduced=window.matchMedia('(prefers-reduced-motion: reduce)');
        // Multiline .heimu cannot use a single nowrap pseudo-element:
        // it piles all copied text onto line one. Project each rendered
        // line into two SHORT clipped chromatic slices only on hover.
        // Range measurements leave the original article DOM and wrapping
        // entirely untouched, including italic/link children.
        const spoilerOverlays=new WeakMap();
        const renderedSpoilerLines=(node)=>{
            const lines=[];
            const walk=document.createTreeWalker(node,NodeFilter.SHOW_TEXT);
            const range=document.createRange();
            let text,budget=0;
            while((text=walk.nextNode())&&budget<340){
                for(let i=0;i<text.length&&budget<340;i++,budget++){
                    const ch=text.nodeValue[i];
                    if(ch==='\n'||ch==='\r')continue;
                    range.setStart(text,i);
                    range.setEnd(text,i+1);
                    const r=range.getBoundingClientRect();
                    if(!r.width||!r.height)continue;
                    let line=lines.find(row=>Math.abs(row.top-r.top)<3);
                    if(!line){
                        line={top:r.top,left:r.left,right:r.right,
                            height:r.height,text:''};
                        lines.push(line);
                    }
                    line.left=Math.min(line.left,r.left);
                    line.right=Math.max(line.right,r.right);
                    line.height=Math.max(line.height,r.height);
                    line.text+=ch;
                }
            }
            range.detach?.();
            return lines.sort((a,b)=>a.top-b.top);
        };
        const spoilerFault=(node)=>{
            if(prefersReduced.matches)return;
            const rects=node.getClientRects();
            if(rects.length<2)return;
            const lines=renderedSpoilerLines(node);
            if(lines.length<2)return;
            node.setAttribute('data-kkpt-multiline','1');
            spoilerOverlays.get(node)?.remove();
            const overlay=document.createElement('div');
            overlay.className='kkpt-heimu-fault';
            overlay.setAttribute('aria-hidden','true');
            const font=getComputedStyle(node);
            for(const row of lines){
                const fragment=document.createElement('span');
                fragment.className='kkpt-heimu-fault-line';
                fragment.dataset.copy=row.text;
                fragment.style.left=row.left+'px';
                fragment.style.top=row.top+'px';
                fragment.style.width=(row.right-row.left+6)+'px';
                fragment.style.height=(row.height+4)+'px';
                fragment.style.fontFamily=font.fontFamily;
                fragment.style.fontSize=font.fontSize;
                fragment.style.fontWeight=font.fontWeight;
                fragment.style.fontStyle=font.fontStyle;
                fragment.style.lineHeight=font.lineHeight;
                fragment.style.letterSpacing=font.letterSpacing;
                overlay.append(fragment);
            }
            document.body.append(overlay);
            spoilerOverlays.set(node,overlay);
        };
        const clearSpoilerFault=(node)=>{
            const overlay=spoilerOverlays.get(node);
            if(!overlay)return;
            spoilerOverlays.delete(node);
            overlay.classList.add('kkpt-fault-away');
            setTimeout(()=>overlay.remove(),210);
        };
        const decorateSpoilers=()=>{
            document.querySelectorAll('span.heimu').forEach(node=>{
                if(node.dataset.kkptBound)return;
                node.dataset.kkptBound='1';
                const label=(node.textContent||'').replace(/\s+/g,' ').trim();
                if(label&&label.length<=240&&!node.children.length)
                    node.setAttribute('data-kkpt-glitch',label);
                node.addEventListener('mouseenter',()=>spoilerFault(node));
                node.addEventListener('mouseleave',()=>clearSpoilerFault(node));
            });
        };
        const decorateLinks=()=>{
            const article=document.querySelector('#mw-content-text,.mw-parser-output');
            if(!article)return;
            article.querySelectorAll('a[href]').forEach(link=>{
                if(link.dataset.kkptLinkReady ||
                    link.classList.contains('kkpt-fate-gear') ||
                    link.querySelector('img,svg,video'))return;
                link.dataset.kkptLinkReady='1';
                link.classList.add('kkpt-link-glitch');
                try{
                    const url=new URL(link.href,document.baseURI);
                    const path=url.pathname.match(/\/wiki\/([^/?#]+)/);
                    const name=url.searchParams.get('title')||
                        (path?decodeURIComponent(path[1]):'');
                    if(url.origin===location.origin &&
                        name.replace(/_/g,' ')==='Kuranoka'){
                        link.classList.add('kkpt-link-origin');
                        // Copy a link only if it truly occupies one
                        // rendered line. Multiline links keep real text.
                        const label=(link.textContent||'').trim();
                        if(!link.children.length &&
                           link.getClientRects().length===1 &&
                           label.length>0&&label.length<100)
                            link.dataset.kkptLinkCopy=label;
                    }
                }catch(_){}
            });
        };
        // All visible references to the old identity are unstable in the
        // Kuronata world, including plain text, table cells and link labels.
        // Wrap only matching TEXT nodes so links keep their original href,
        // MediaWiki tables/collapsibles keep their layout, and wiki editing
        // controls remain untouched.
        const decorateIdentityMentions=()=>{
            const article=document.querySelector('#mw-content-text,.mw-parser-output');
            if(!article)return;
            const hasIdentity=/Kuranoka|Kurano\s+Kanata|天野[ \u00a0\u3000]*彼方/i;
            const exactIdentity=/Kuranoka|Kurano\s+Kanata|天野[ \u00a0\u3000]*彼方/gi;
            const walker=document.createTreeWalker(article,NodeFilter.SHOW_TEXT,{
                acceptNode(node){
                    if(!node.nodeValue||!hasIdentity.test(node.nodeValue))
                        return NodeFilter.FILTER_REJECT;
                    const parent=node.parentElement;
                    if(!parent||parent.closest('script,style,textarea,code,pre,'+
                        'input,button,select,[contenteditable="true"],'+
                        '.kkpt-identity-glitch,.kkpt-heimu-fault,'+
                        'span.heimu,a.kkpt-link-origin,'+
                        '#kkpt-afterglow,#kkpt-toggle'))
                        return NodeFilter.FILTER_REJECT;
                    return NodeFilter.FILTER_ACCEPT;
                }
            });
            const matches=[];
            let node;
            while((node=walker.nextNode())&&matches.length<1800)
                matches.push(node);
            let index=0;
            for(const textNode of matches){
                const raw=textNode.nodeValue;
                const fragment=document.createDocumentFragment();
                let previous=0,match;
                exactIdentity.lastIndex=0;
                while((match=exactIdentity.exec(raw))){
                    if(match.index>previous)
                        fragment.append(document.createTextNode(
                            raw.slice(previous,match.index)));
                    const el=document.createElement('span');
                    el.className='kkpt-identity-glitch';
                    el.dataset.kkptIdentity=match[0];
                    el.textContent=match[0];
                    el.style.setProperty('--kkpt-identity-delay',
                        (-((index++*7)%23)*.21).toFixed(2)+'s');
                    fragment.append(el);
                    previous=match.index+match[0].length;
                }
                if(previous<raw.length)
                    fragment.append(document.createTextNode(raw.slice(previous)));
                textNode.replaceWith(fragment);
            }
        };
        const createAmbience=()=>{
            if(prefersReduced.matches||document.getElementById('kkpt-afterglow')||!document.body)return;
            const overlay=document.createElement('div');
            overlay.id='kkpt-afterglow';
            overlay.setAttribute('aria-hidden','true');
            const el=(type,i)=>{
                const part=document.createElement('span');
                part.className=type==='soot'?'kkpt-soot-cell':'kkpt-ash-cell';
                const smoke=type==='soot';
                // All sprites are static layers with compositor-only
                // transform/opacity animation. No persistent canvas or RAF.
                // The soot is a side-bank haze, not a random full-screen
                // spread of isolated circular clouds.
                const fromLeft=i%2===0;
                part.style.left=(smoke
                    ? (fromLeft?-26+Math.random()*22:79+Math.random()*21)
                    : Math.random()*100)+'%';
                part.style.top=(smoke?8+Math.random()*94:15+Math.random()*94)+'%';
                part.style.setProperty('--size',(smoke?220+Math.random()*240:2+Math.random()*4).toFixed(1)+'px');
                part.style.setProperty('--delay',(-Math.random()*(smoke?29:18)).toFixed(2)+'s');
                part.style.setProperty('--duration',(smoke?18+Math.random()*14:8+Math.random()*11).toFixed(2)+'s');
                part.style.setProperty('--wind',((Math.random()-.5)*(smoke?100:230)).toFixed(1)+'px');
                return part;
            };
            for(let i=0;i<(innerWidth<700?8:16);i++)overlay.append(el('soot',i));
            for(let i=0;i<30;i++)overlay.append(el('ash',i));
            document.body.append(overlay);
        };
        const init=()=>{
            decorateSpoilers();
            decorateLinks();
            decorateIdentityMentions();
            createAmbience();
            mw.hook('wikipage.content').add(()=>{
                decorateSpoilers();
                decorateLinks();
                decorateIdentityMentions();
            });
        };
        if(document.readyState==='loading')
            document.addEventListener('DOMContentLoaded',init,{once:true});
        else init();

        // One brief spatial fault roughly every 14-36 seconds, never a
        // full-screen white strobe. Pause while the iframe is hidden.
        const pulse=()=>{
            const inactive=document.hidden||prefersReduced.matches||
                root.classList.contains('kkpt-frame-inactive')||
                root.classList.contains('kkpt-world-suspended')||
                (window!==window.top&&window.frameElement?.getAttribute('aria-hidden')==='true');
            if(!inactive){
                root.style.setProperty('--kkpt-rift-y',(14+Math.random()*70).toFixed(1)+'%');
                root.classList.add('kkpt-rift');
                window.setTimeout(()=>root.classList.remove('kkpt-rift'),390);
            }
            window.setTimeout(pulse,5000+Math.random()*15000);
        };
        window.setTimeout(pulse,5000+Math.random()*15000);
    }
    installKuronataAfterglow();

    // The nested preview only applies its own theme; no recursive iframe.
    if (window!==window.top || window.__kkptV12) return;
    window.__kkptV12=true;
    window.__kkptVersion='31.0';

    // Easter eggs + Infobox gear are the default. No floating pill.
    const SHOW_FLOATING_BUTTON=false;
    const otherPage=basePage==='Kuranoka'?'Kuronata':'Kuranoka';
    const baseUrl=location.href;
    const baseTitle=document.title;
    const otherUrl=new URL('/wiki/'+encodeURIComponent(otherPage),location.href);
    const clipSide=basePage==='Kuranoka'?'right':'left';
    const hideClip=clipSide==='right'?'inset(0 0 0 100%)':'inset(0 100% 0 0)';
    const sleep=ms=>new Promise(r=>setTimeout(r,ms));
    const smooth=t=>t*t*(3-2*t);
    const imagePool=new Map();
    // V24: preload both original background photographs. The target
    // image is decoded while its real-document iframe is preparing,
    // reducing flashes of the bare background-color at navigation.
    const worldBackdrops={
        Kuranoka:'https://blockland.wiki/images/0/05/%E7%A7%AF%E9%9B%A8%E4%BA%911.png',
        Kuronata:'https://blockland.wiki/images/a/ab/%E9%BB%84%E6%98%8F%EF%BC%8C%E9%BB%91%E4%BA%91.png'
    };
    function primeWorldBackdrops(){
        const current=worldBackdrops[basePage];
        if(current&&document.head){
            const link=document.createElement('link');
            link.rel='preload';
            link.as='image';
            link.href=current;
            link.setAttribute('fetchpriority','high');
            link.dataset.kkptBackgroundPreload='1';
            document.head.appendChild(link);
            warmImage(current).catch(()=>{});
        }
        // Give the current photo first priority; then prepare the next
        // world so the iframe and the eventual real page can reuse it.
        setTimeout(()=>{
            const next=worldBackdrops[otherPage];
            if(next)warmImage(next).catch(()=>{});
        },300);
    }
    primeWorldBackdrops();

    const ENABLE_TRANSITION_AUDIO = true;
    const FIRE_VOLUME = .30;
    const DAWN_VOLUME = .20;
    let soundContext=null,fireBuffer=null,activeSound=null;

    // Public-domain PADsynth recording, ~8.4s / 120KB. Change this
    // to a same-origin Wiki-upload URL if external media are blocked.
    const REBIRTH_PAD_URL=
        'https://upload.wikimedia.org/wikipedia/commons/e/ed/Padsynth_example_synth_piano.ogg';
    let padBytesPromise=null,padDecodePromise=null,padBuffer=null;
    function preloadRebirthPad(){
        if(padBytesPromise)return padBytesPromise;
        padBytesPromise=fetch(REBIRTH_PAD_URL,{mode:'cors',cache:'force-cache'})
            .then(resp=>{
                if(!resp.ok)throw new Error('PAD HTTP '+resp.status);
                return resp.arrayBuffer();
            })
            .catch(err=>{
                console.debug('[KKPT] PAD file unavailable:',err);
                return null;
            });
        return padBytesPromise;
    }
    function decodeRebirthPad(ctx){
        if(padBuffer)return Promise.resolve(padBuffer);
        if(!padDecodePromise){
            padDecodePromise=preloadRebirthPad()
                .then(bytes=>bytes?ctx.decodeAudioData(bytes.slice(0)):null)
                .then(result=>(padBuffer=result))
                .catch(err=>{
                    console.debug('[KKPT] Cannot decode PAD:',err);
                    return null;
                });
        }
        return padDecodePromise;
    }
    // A plain media element can still play the recording when a site's
    // CORS policy disallows reading the file into Web Audio.
    function playRebirthPadFallback(durationMs){
        const sound=new Audio(REBIRTH_PAD_URL);
        sound.volume=0;
        sound.play().then(()=>{
            const begin=performance.now();
            const timer=setInterval(()=>{
                const t=Math.min(1,(performance.now()-begin)/durationMs);
                sound.volume=Math.max(0,Math.min(DAWN_VOLUME,
                    DAWN_VOLUME*Math.min(t/.27,(1-t)/.26)));
                if(t>=1){clearInterval(timer);sound.pause();sound.src='';}
            },80);
        }).catch(err=>console.debug('[KKPT] PAD playback unavailable:',err));
    }

    function primeSound(){
        if(!ENABLE_TRANSITION_AUDIO)return;
        try{
            const AudioEngine=window.AudioContext||window.webkitAudioContext;
            if(!AudioEngine)return;
            if(!soundContext)soundContext=new AudioEngine();
            if(soundContext.state==='suspended')soundContext.resume().catch(()=>{});
            decodeRebirthPad(soundContext);
        }catch(err){console.debug('[KKPT] Audio unavailable:',err);}
    }
    function createFireAudio(ctx){
        const length=Math.round(ctx.sampleRate*4.5);
        const buffer=ctx.createBuffer(1,length,ctx.sampleRate);
        const data=buffer.getChannelData(0);
        let low=0,middle=0;
        for(let i=0;i<length;i++){
            const random=Math.random()*2-1;
            low=low*.992+random*.008;
            middle=middle*.92+random*.08;
            data[i]=Math.max(-1,Math.min(1,
                low*3.9+middle*.33+random*.055));
        }
        // Micro-crackles: impulsive bursts with different decay times.
        for(let k=0;k<350;k++){
            const at=Math.floor(Math.random()*(length-1500));
            const decay=36+Math.random()*330;
            const duration=Math.min(1400,Math.ceil(decay*4));
            const power=.20+Math.pow(Math.random(),3)*.68;
            for(let j=0;j<duration;j++){
                const env=Math.exp(-j/decay);
                data[at+j]=Math.max(-1,Math.min(1,data[at+j]+
                    (Math.random()*2-1)*power*env));
            }
        }
        return buffer;
    }
    function transitionSound(dark,durationMs){
        const ctx=soundContext;
        if(!ctx||ctx.state!=='running')return;
        const start=ctx.currentTime+.018;
        const span=durationMs/1000;
        if(activeSound){
            const old=activeSound.gain;
            old.cancelScheduledValues(start);
            old.setTargetAtTime(.0001,start,.05);
        }
        const master=ctx.createGain();
        master.gain.setValueAtTime(.0001,start);
        master.gain.linearRampToValueAtTime(dark?FIRE_VOLUME:DAWN_VOLUME,
            start+(dark?.75:1.10));
        master.gain.setValueAtTime(dark?FIRE_VOLUME:DAWN_VOLUME,
            start+span-(dark?.88:1.0));
        master.gain.exponentialRampToValueAtTime(.0001,start+span);
        master.connect(ctx.destination);
        activeSound={gain:master};
        if(dark){
            if(!fireBuffer)fireBuffer=createFireAudio(ctx);
            const src=ctx.createBufferSource();
            src.buffer=fireBuffer;src.loop=true;
            const lowpass=ctx.createBiquadFilter();
            lowpass.type='lowpass';lowpass.frequency.value=2050;
            const bass=ctx.createBiquadFilter();
            bass.type='highpass';bass.frequency.value=55;
            src.connect(lowpass);lowpass.connect(bass);bass.connect(master);
            src.start(start);src.stop(start+span+.12);
        }else{
            // A REAL recorded PADsynth sample; no generated wind-chimes.
            decodeRebirthPad(ctx).then(buffer=>{
                if(!buffer){playRebirthPadFallback(durationMs);return;}
                const at=Math.max(start,ctx.currentTime+.020);
                if(at>start+span-.55)return;
                const player=ctx.createBufferSource();
                player.buffer=buffer;
                player.connect(master);
                player.start(at,Math.max(0,at-start)+.95);
                player.stop(start+span);
            }).catch(()=>{});
        }
        setTimeout(()=>{
            if(activeSound&&activeSound.gain===master)activeSound=null;
            try{master.disconnect();}catch(_){}
        },durationMs+350);
    }

    let active = false; // true only during the visual handoff; destination navigates natively
    let animating = false;
    let gearPending = false;
    let ready = false;
    let loading = null;
    let button, labelTitle, labelSub, labelIcon, frame;
    let otherTitle = otherPage + ' - Blockland Wiki';

    function whichPage() { return active ? otherPage : basePage; }
    function destination() { return active ? basePage : otherPage; }
    function isDark(page) { return page === 'Kuronata'; }
    function pathPage() {
        const url = new URL(location.href);
        if (url.pathname.startsWith('/wiki/')) {
            try { return decodeURIComponent(url.pathname.slice(6)).replace(/_/g, ' '); }
            catch (e) { return ''; }
        }
        return url.searchParams.get('title') || '';
    }

    function updateButton() {
        if (!button) return;
        const to = destination();
        button.href = to === basePage ? baseUrl : otherUrl.href;
        labelTitle.textContent = to.toUpperCase();
        labelSub.textContent = isDark(to) ? 'BURN THE SKY' : 'RECLAIM THE SKY';
        labelIcon.textContent = isDark(to) ? '✦' : '❄';
        button.classList.toggle('kkpt-dark', isDark(whichPage()));
        button.setAttribute('aria-label', isDark(to) ? '燃尽天空,进入 Kuronata' : '驱散黑暗,回到 Kuranoka');
    }

    // Accept the two standard MediaWiki link forms, while rejecting
    // edit/action links, external sites and similarly named articles.
    function wikiLinkPage(anchor, doc) {
        try {
            const url = new URL(anchor.href, doc.baseURI);
            if (url.origin !== location.origin) return null;
            const action = url.searchParams.get('action');
            if (action && action !== 'view') return null;
            let title = url.searchParams.get('title');
            if (!title) {
                const matched = url.pathname.match(/^\/wiki\/([^/?#]+)\/?$/);
                if (matched) title = decodeURIComponent(matched[1]);
            }
            title = (title || '').replace(/_/g, ' ');
            return title === 'Kuranoka' || title === 'Kuronata' ? title : null;
        } catch (_) {
            return null;
        }
    }

    function decoratePortalLinks(doc, targetPage) {
        // Use only the article: sidebar, edit tools and site-wide links
        // must retain their usual navigation behavior.
        const content = doc.querySelector('#mw-content-text,.mw-parser-output');
        if (!content) return;
        content.querySelectorAll('a[href]').forEach(anchor => {
            if(anchor.classList.contains('kkpt-fate-gear'))return;
            if (wikiLinkPage(anchor, doc) !== targetPage) return;
            anchor.classList.add('kkpt-portal-link');
            anchor.classList.toggle('kkpt-portal-red', targetPage === 'Kuronata');
            anchor.classList.toggle('kkpt-portal-blue', targetPage === 'Kuranoka');
            const caption = (anchor.textContent || '').trim();
            if (caption) anchor.dataset.kkptText = caption.slice(0, 120);
            anchor.setAttribute('aria-label', caption + ',切换至 ' + targetPage);
        });
    }

    function watchPortalLinks(doc, targetPage) {
        decoratePortalLinks(doc, targetPage);
        if (doc.__kkptPortalObserver) return;
        const root = doc.querySelector('#mw-content-text,.mw-parser-output');
        if (!root) return;
        let pending=false;
        const observer = new MutationObserver(() => {
            if(pending)return;
            pending=true;
            setTimeout(()=>{
                pending=false;
                decoratePortalLinks(doc,targetPage);
            },120);
        });
        observer.observe(root, {childList:true,subtree:true});
        doc.__kkptPortalObserver = observer;
    }

    function isPlainClick(event) {
        return !event.defaultPrevented && event.button === 0 &&
            !event.ctrlKey && !event.metaKey && !event.altKey && !event.shiftKey;
    }

    function findAnchor(event, doc) {
        const target = event.target;
        return target && target.nodeType === 1 &&
            typeof target.closest === 'function'
            ? target.closest('a[href]') : null;
    }

    function portalClick(event, doc, targetPage, nextActive) {
        if (!isPlainClick(event)) return false;
        const anchor = findAnchor(event, doc);
        if (!anchor || (anchor.target && anchor.target !== '_self') ||
            anchor.hasAttribute('download') ||
            wikiLinkPage(anchor, doc) !== targetPage) return false;
        event.preventDefault();
        primeSound(); // Synchronous click activation unlocks Web Audio.
        if(anchor.classList.contains('kkpt-fate-gear')) {
            beginFateSwap(anchor,nextActive);
        } else {
            requestSwap(nextActive);
        }
        return true;
    }

    // The Infobox gear begins to turn before the actual world changes.
    function beginFateSwap(anchor,nextActive) {
        if(animating||gearPending||nextActive===active)return;
        gearPending=true;
        anchor.classList.add('kkpt-fate-gear-turning');
        setTimeout(()=>{
            gearPending=false;
            requestSwap(nextActive);
        },570);
        setTimeout(()=>anchor.classList.remove('kkpt-fate-gear-turning'),4800);
    }

    function fateGearShape() {
        const parts=[];
        for(let i=0;i<48;i++) {
            const a=i/48*Math.PI*2-Math.PI/2;
            const r=(i%4===0||i%4===3)?21:16.8;
            parts.push((i?'L':'M')+(24+Math.cos(a)*r).toFixed(2)+' '+
                (24+Math.sin(a)*r).toFixed(2));
        }
        return parts.join(' ')+' Z';
    }

    function mountFateGear(doc,targetPage) {
        if(doc.querySelector('.kkpt-fate-gear'))return;
        const content=doc.querySelector('#mw-content-text,.mw-parser-output');
        if(!content)return;
        // The fate wheel stays inside the native Infobox caption, but is
        // positioned independently: it must NEVER push the title off-center.
        const box=content.querySelector('table.infobox.vcard,table.infobox');
        const host=box?.caption ||
            box?.querySelector('th.infobox-above,th.infobox-title,th[colspan]')||
            doc.querySelector('#firstHeading .mw-page-title-main,'+
                '.mw-page-title-main,#firstHeading');
        if(!host)return;
        host.classList.add('kkpt-fate-host');
        const anchor=doc.createElement('a');
        anchor.className='kkpt-fate-gear';
        anchor.href=new URL('/wiki/'+targetPage,doc.baseURI).href;
        anchor.title=targetPage==='Kuronata'
            ?'命运的齿轮 · 唤醒 Kuronata':'命运的齿轮 · 回到 Kuranoka';
        anchor.setAttribute('aria-label',anchor.title);
        anchor.innerHTML='<svg class="kkpt-fate-gear-svg" viewBox="0 0 48 48" '+
            'aria-hidden="true" focusable="false"><path d="'+fateGearShape()+
            '"/><circle cx="24" cy="24" r="8.5"/>'+
            '<circle cx="24" cy="24" r="3"/></svg>';
        // Critical inline dimensions: if page-specific CSS arrives late,
        // a raw SVG must NEVER expand into the giant black gear again.
        host.style.position='relative';
        anchor.style.cssText='position:absolute;right:7px;top:7px;'+
            'width:26px;height:26px;padding:4px;box-sizing:border-box;'+
            'display:grid;place-items:center;float:none;z-index:3;'+
            'color:#e5eff5;background:rgba(30,45,60,.35);'+
            'border:1px solid rgba(255,255,255,.30);border-radius:50%';
        anchor.firstElementChild?.setAttribute('width','100%');
        anchor.firstElementChild?.setAttribute('height','100%');
        host.appendChild(anchor);

        // Fixed corner placement: no title measurements, ResizeObserver
        // or reflow during the animation.
    }

    // Read backgrounds after background-template code populates --bg-image.
    function backgroundUrls(doc) {
        const urls = new Set();
        const selector = [doc.documentElement, doc.body];
        try {
            doc.querySelectorAll('.background-theme,[class*="background"],[style*="background"],#mw-content-text,.citizen-page-container')
                .forEach((el, i) => { if (i < 18) selector.push(el); });
        } catch (e) { /* use html/body */ }
        function add(value) {
            if (!value) return;
            const pattern = /url\(\s*(['"]?)(.*?)\1\s*\)/gi;
            let match;
            while ((match = pattern.exec(value))) {
                try { urls.add(new URL(match[2], doc.baseURI).href); } catch (e) { /* ignore */ }
            }
            if (/^https?:\/\/\S+\.(?:jpg|jpeg|png|webp|avif)(?:\?\S*)?$/i.test(value)) {
                try { urls.add(new URL(value, doc.baseURI).href); } catch (e) { /* ignore */ }
            }
        }
        selector.forEach(el => {
            if (!el) return;
            try {
                [null, '::before', '::after'].forEach(pseudo => {
                    const style = doc.defaultView.getComputedStyle(el, pseudo);
                    if (!style) return;
                    add(style.backgroundImage);
                    add(style.getPropertyValue('--bg-image'));
                    add(style.getPropertyValue('--background-image'));
                });
                if (el.dataset) add(el.dataset.bgImage);
            } catch (e) { /* style not yet ready */ }
        });
        return [...urls];
    }

    function warmImage(url) {
        if (imagePool.has(url)) return imagePool.get(url).promise;
        const image = new Image();
        const promise = new Promise(resolve => {
            let finished = false;
            const timeout = setTimeout(() => done(false), 5000);
            function done(ok) {
                if (finished) return;
                finished = true;
                clearTimeout(timeout);
                resolve(ok);
            }
            image.onload = () => done(true);
            image.onerror = () => done(false);
            image.src = url;
            if (image.complete) done(image.naturalWidth > 0);
        }).then(ok => ok && image.decode
            ? Promise.race([image.decode().then(() => true).catch(() => true),sleep(900).then(() => true)])
            : ok);
        imagePool.set(url, { image, promise });
        return promise;
    }

    async function warmBackgrounds(doc) {
        const urls = backgroundUrls(doc);
        await Promise.allSettled(urls.map(warmImage));
    }

    function wireFrame() {
        try {
            const doc = frame.contentDocument;
            if (!doc) return;
            otherTitle = doc.title || otherTitle;
            // The preview exists only for the animated reveal. Pausing
            // its hidden ambience avoids doubling ongoing render work.
            doc.documentElement.classList.add('kkpt-frame-inactive');
            watchPortalLinks(doc, basePage);
            mountFateGear(doc, basePage);
            if (doc.__kkptFrameBridge) return;
            doc.__kkptFrameBridge = true;

            // Non-anchor navigation should leave the iframe and open normally
            // in the top window, so the browser's URL doesn't become stale.
            doc.addEventListener('click', event => {
                if (!active || !isPlainClick(event)) return;
                if (portalClick(event, doc, basePage, false)) return;
                const el = findAnchor(event, doc);
                if (!el || (el.target && el.target !== '_self')) return;
                const href = el.href;
                if (!href || href.startsWith('javascript:')) return;
                const next = new URL(href, doc.baseURI);
                // Same-document fragments stay inside the temporary preview.
                const currentFrame = new URL(frame.contentWindow.location.href);
                if (next.origin === currentFrame.origin &&
                    next.pathname === currentFrame.pathname &&
                    next.search === currentFrame.search && next.hash) {
                    history.replaceState(history.state, '', next.href);
                    return;
                }
                event.preventDefault();
                navigateRealPage(next.href);
            }, true);

            doc.addEventListener('submit', event => {
                if (active && event.target instanceof doc.defaultView.HTMLFormElement) {
                    event.target.target = '_top';
                }
            }, true);
        } catch (err) {
            console.warn('[KuranokaPageTransition] Frame link bridge unavailable:', err);
        }
    }

    function warmFrame() {
        if (loading) return loading;
        frame = document.createElement('iframe');
        frame.id = 'kkpt-preview';
        frame.src = otherUrl.href; // set BEFORE insertion, avoids extra initial history hop
        frame.title = otherPage + ' 预载页面';
        frame.tabIndex = -1;
        frame.setAttribute('aria-hidden', 'true');
        frame.setAttribute('loading', 'eager');
        frame.style.clipPath = hideClip;
        // Load all resources in advance, but don't composite the hidden
        // full-screen Wiki until its first transition frame.
        frame.style.visibility = 'hidden';

        loading = new Promise(resolve => {
            let settled = false;
            let preparing = false;
            let poll = null;
            function finish(ok, reason) {
                if (settled) return;
                settled = true;
                clearInterval(poll);
                ready = ok;
                if (!ok) console.warn('[KuranokaPageTransition] Preview:', reason);
                resolve(ok);
            }
            async function inspect() {
                if (settled || preparing) return;
                try {
                    const doc = frame.contentDocument;
                    if (!doc || !doc.querySelector('#mw-content-text,.mw-parser-output')) return;
                    preparing = true;
                    clearInterval(poll);
                    await sleep(320); // Background.js / wiki style scripts
                    await Promise.race([warmBackgrounds(doc), sleep(3600)]);
                    await sleep(120);
                    await Promise.race([warmBackgrounds(doc), sleep(1300)]);
                    frame.contentWindow.scrollTo(0, 0);
                    wireFrame();
                    finish(true);
                } catch (err) { finish(false, String(err)); }
            }
            frame.addEventListener('load', () => {
                if (!settled && !preparing) inspect();
            });
            frame.addEventListener('error', () => finish(false,'iframe 网络加载错误'));
            document.body.append(frame);
            poll = setInterval(inspect, 130);
            setTimeout(() => { if (!settled && !preparing) finish(false,'18 秒仍未找到目标正文'); }, 18000);
        });

        warmBackgrounds(document).catch(() => {});
        setTimeout(() => warmBackgrounds(document).catch(() => {}), 700);
        return loading;
    }


    // Shared, low-resolution atmospherics: return of V14's dark smoke,
    // long-lived torn paper, shockwaves, blue-white petals and pollen.
    // Only the combustion CURTAIN is replaced by the bright V2 engine.
    let atmosphereAssetCache=null;
    const atmosphereNoiseCache=new Map();
    function createAtmosphere(canvas,buildOneOnly=false,foreground=null) {
        // V30: background soot never touches the canvas above the GPU flame.
        const backCtx=canvas.getContext('2d',{alpha:true});
        const fireCtx=foreground?.getContext('2d',{alpha:true})||null;
        let ctx=backCtx;
        const rand = n => {
            const cached=atmosphereNoiseCache.get(n);
            if(cached!==undefined)return cached;
            const x = Math.sin(n*127.1+311.7)*43758.5453123;
            const value=x-Math.floor(x);
            atmosphereNoiseCache.set(n,value);
            return value;
        };
        const clamp01 = n => Math.max(0,Math.min(1,n));
        function valueNoise(x,y,seed) {
            const ix=Math.floor(x), iy=Math.floor(y);
            let fx=x-ix,fy=y-iy;
            fx=fx*fx*(3-2*fx);fy=fy*fy*(3-2*fy);
            const h=(a,b)=>rand(a*171.3+b*513.7+seed*89.1);
            const a=h(ix,iy)*(1-fx)+h(ix+1,iy)*fx;
            const b=h(ix,iy+1)*(1-fx)+h(ix+1,iy+1)*fx;
            return a*(1-fy)+b*fy;
        }
        function smokeTexture(seed,dark) {
            const tex=document.createElement('canvas');
            tex.width=tex.height=112;
            const g=tex.getContext('2d');
            const data=g.createImageData(112,112);
            for(let y=0;y<112;y++) for(let x=0;x<112;x++){
                const u=(x-56)/56,v=(y-56)/56;
                const curl=valueNoise(u*2.9+11,v*2.9+1,seed);
                const curl2=valueNoise(u*3.4+3,v*3.4+7,seed+7);
                const wx=u+.47*(curl-.5),wy=v+.40*(curl2-.5);
                const radius=Math.sqrt(wx*wx*.91+wy*wy*1.13);
                const envelope=clamp01((1.05-radius)/.56);
                const low=valueNoise(u*4.1+4,v*4.1-9,seed+2);
                const high=valueNoise(u*11.4-3,v*11.4+6,seed+5);
                const fibers=valueNoise(u*22.0+1,v*16.0+5,seed+9);
                const density=clamp01((low*.62+high*.28+fibers*.10-.28)*2.0)*
                    envelope*envelope;
                const i=(y*112+x)*4;
                const variation=low*28+high*15;
                if(dark){
                    data.data[i]=5+variation*.37;
                    data.data[i+1]=5+variation*.33;
                    data.data[i+2]=8+variation*.38;
                }else{
                    data.data[i]=44+variation;
                    data.data[i+1]=91+variation;
                    data.data[i+2]=125+variation;
                }
                data.data[i+3]=Math.round(240*density);
            }
            g.putImageData(data,0,0);
            return tex;
        }
        // V2-inspired white-hot additive sprites, but with noise-eroded
        // silhouettes instead of repetitive smooth, elliptical balls.
        function glowTexture(seed,mode) {
            const tex=document.createElement('canvas');
            tex.width=96;tex.height=128;
            const g=tex.getContext('2d');
            const gradient=g.createRadialGradient(48,68,0,48,68,64);
            const colors=mode==='fire'
                ? [[0,'#fffef1'],[.14,'#fff4bb'],[.34,'#ffd04d'],
                   [.55,'#ff841bcc'],[.80,'#bc290749'],[1,'#6e030000']]
                : mode==='blue'
                ? [[0,'#ffffff'],[.19,'#f1ffff'],[.40,'#a2efff'],
                   [.68,'#5298ff99'],[1,'#345bf000']]
                : [[0,'#ffffff'],[.19,'#fff8cd'],[.49,'#ff9b28cc'],
                   [1,'#ff380000']];
            colors.forEach(([p,c])=>gradient.addColorStop(p,c));
            g.fillStyle=gradient;g.fillRect(0,0,96,128);
            const img=g.getImageData(0,0,96,128);
            for(let y=0;y<128;y++)for(let x=0;x<96;x++){
                const u=(x-48)/48,v=(y-64)/64;
                const cloud=valueNoise(u*4+seed*1.9,v*4+seed*.7,seed+18);
                const fiber=valueNoise(u*11+3,v*8+17,seed+41);
                const shifted=u+.18*(cloud-.5);
                const irregular=clamp01((1.15-Math.abs(shifted))/.52)*
                    clamp01((1.05-Math.abs(v+.12*(fiber-.5)))/.42);
                const n=.59+.77*cloud+.28*fiber;
                const alphaIndex=(y*96+x)*4+3;
                img.data[alphaIndex]=Math.round(img.data[alphaIndex]*
                    irregular*clamp01(n));
            }
            g.putImageData(img,0,0);
            return tex;
        }
        // V25: the profiler found one 270ms long task here. Build the
        // EXACT SAME 17 textures in separate tasks, never all at once.
        // The stable noise cache avoids repeating the costly sin hash.
        const cache=atmosphereAssetCache ||= {
            sootSprites:[],mistSprites:[],FIRE_GLOW:[],BLUE_GLOW:[],
            EMBER_GLOW:null
        };
        function buildNextAsset(){
            let n=cache.sootSprites.length;
            if(n<4){cache.sootSprites.push(smokeTexture(n+17,true));return true;}
            n=cache.mistSprites.length;
            if(n<4){cache.mistSprites.push(smokeTexture(n+51,false));return true;}
            n=cache.FIRE_GLOW.length;
            if(n<4){cache.FIRE_GLOW.push(glowTexture(n+1,'fire'));return true;}
            n=cache.BLUE_GLOW.length;
            if(n<4){cache.BLUE_GLOW.push(glowTexture(n+8,'blue'));return true;}
            if(!cache.EMBER_GLOW){
                cache.EMBER_GLOW=glowTexture(21,'ember');return true;
            }
            return false;
        }
        if(buildOneOnly)return buildNextAsset();
        // Normally prewarming is already complete before a user clicks.
        // The fallback also works if an animation is started immediately.
        while(buildNextAsset()){}
        const {sootSprites,mistSprites,FIRE_GLOW,BLUE_GLOW,EMBER_GLOW}=cache;
        const combustion=[];
        const residualSoot=[];
        const tornPaper=[];
        let lastElapsed=0,spawnRemainder=0,sootRemainder=0,shardRemainder=0;
        function advanceCombustion(seconds,progress,dark,elapsed,w,h) {
            const dt=Math.min(.065,Math.max(0,elapsed-lastElapsed));
            lastElapsed=elapsed;
            const live=progress>.01&&progress<.985;
            if(live){
                // Restore the actual V13 flame density: the V27 reduction
                // from 370 to 70 removed most of P3's oppressive fire wall.
                const flow=(dark?370:115)*Math.min(1.5,h/720)*
                    (.75+.25*Math.sin(Math.PI*progress));
                spawnRemainder+=dt*flow;
                const births=Math.min(65,Math.floor(spawnRemainder));
                spawnRemainder-=births;
                for(let j=0;j<births&&combustion.length<1320;j++){
                    const y=Math.random()*h;
                    const edge=edgeAt(y,seconds,progress,w);
                    const r=Math.random();
                    const kind=dark
                        ? r<.36?'flame':r<.89?'ember':'ash'
                        : r<.37?'glow':r<.81?'leaf':'pollen';
                    const small=kind==='ember'||kind==='pollen';
                    const soot=kind==='ash';
                    const life=dark
                        ? (soot?.7+Math.random()*1.4:
                            small?1.05+Math.random()*1.75:.42+Math.random()*.76)
                        : 1.15+Math.random()*1.55;
                    combustion.push({
                        kind,x:edge+(dark?1:-1)*(Math.random()*47-8),
                        y:y+(Math.random()-.5)*25,
                        vx:(dark?1:-1)*(dark?(small?85+Math.random()*320:
                            14+Math.random()*154):
                            16+Math.random()*69),
                        vy:-(dark?(small?12+Math.random()*205:
                            32+Math.random()*171):12+Math.random()*57),
                        life,remaining:life,
                        radius:dark
                            ? (soot?1.2+Math.random()*2.7:
                                small?2+Math.random()*4.8:9+Math.random()*19)
                            : kind==='glow'?26+Math.random()*49:
                                kind==='leaf'?4+Math.random()*6:
                                2+Math.random()*3,
                        angle:(Math.random()-.5)*1.1,
                        sprite:(Math.random()*4)|0,
                        seed:Math.random()*6.28
                    });
                }
                if(dark) {
                    // Unlike the traveling front, these black smoke plumes
                    // are born in world-space and remain over burnt paper.
                    sootRemainder+=dt*(h<680?41:62);
                    const sootBirths=Math.min(11,Math.floor(sootRemainder));
                    sootRemainder-=sootBirths;
                    for(let i=0;i<sootBirths&&residualSoot.length<(w<700?125:225);i++){
                        const y=Math.random()*h;
                        const life=2.15+Math.random()*1.60;
                        residualSoot.push({
                            x:edgeAt(y,seconds,progress,w)+5+Math.random()*83,
                            y:y+(Math.random()-.5)*48,
                            vx:8+Math.random()*39,vy:-18-Math.random()*83,
                            size:155+Math.random()*195,life,remaining:life,
                            sprite:(Math.random()*4)|0,
                            spin:(Math.random()-.5)*.8,
                            seed:Math.random()*6.28
                        });
                    }
                    // Charcoal sheets tear off in irregular polygons, not
                    // squares or narrow glitch streaks.
                    shardRemainder+=dt*(h<680?41:69);
                    const shardBirths=Math.min(13,Math.floor(shardRemainder));
                    shardRemainder-=shardBirths;
                    for(let i=0;i<shardBirths&&tornPaper.length<330;i++){
                        const y=Math.random()*h;
                        const life=1.00+Math.random()*2.05;
                        const points=8+Math.floor(Math.random()*8);
                        const outline=Array.from({length:points},(_,j)=>({
                            a:Math.PI*2*j/points+(Math.random()-.5)*.52,
                            r:.20+Math.random()*1.16
                        }));
                        tornPaper.push({
                            x:edgeAt(y,seconds,progress,w)+(Math.random()-.2)*66,
                            y, vx:58+Math.random()*330,
                            vy:-210+Math.random()*295,
                            gravity:90+Math.random()*150,
                            radius:2+Math.pow(Math.random(),2.7)*23,
                            angle:Math.random()*6.28,
                            spin:(Math.random()-.5)*7,
                            outline,life,remaining:life,
                            seed:Math.random()*6.28
                        });
                    }
                }
            }
            for(let i=combustion.length-1;i>=0;i--){
                const p=combustion[i];
                p.remaining-=dt;
                if(p.remaining<=0){combustion.splice(i,1);continue;}
                p.x+=(p.vx+Math.sin(elapsed*(dark?5:1.6)+p.seed)*
                    (dark?22:24))*dt;
                p.y+=p.vy*dt;
                p.vy-=(dark?17:7)*dt;
            }
            for(let i=residualSoot.length-1;i>=0;i--){
                const p=residualSoot[i];
                p.remaining-=dt;
                if(p.remaining<=0){residualSoot.splice(i,1);continue;}
                p.x+=(p.vx+Math.sin(elapsed*2+p.seed)*27)*dt;
                p.y+=p.vy*dt;
                p.size+=32*dt;
            }
            for(let i=tornPaper.length-1;i>=0;i--){
                const p=tornPaper[i];
                p.remaining-=dt;
                if(p.remaining<=0){tornPaper.splice(i,1);continue;}
                p.x+=(p.vx+Math.sin(elapsed*4+p.seed)*42)*dt;
                p.y+=p.vy*dt;
                p.vy+=p.gravity*dt;
                p.angle+=p.spin*dt;
            }
        }
        const particles=Array.from({length:innerWidth<700?54:85},(_,i)=>({
            seed:rand(i*4+71),height:rand(i*5+13),
            lifetime:.5+rand(i*8+37)*.7,
            phase:rand(i*9+21),sprite:i%4,
            scale:.72+rand(i*7+9)*1.25,
            bend:rand(i*15+23)*6.28
        }));
        const motes=Array.from({length:innerWidth<700?92:175},(_,i)=>({
            y:rand(i*3+17),phase:rand(i*9+43),
            speed:105+rand(i*12+5)*410,
            drift:90+rand(i*15+2)*460,
            length:5+rand(i*17+7)*26
        }));
        const shockDebris=Array.from({length:innerWidth<700?40:85},(_,i)=>({
            angle:rand(i*17+131)*Math.PI*2,
            velocity:190+rand(i*11+51)*900,
            seed:rand(i*5+79),
            length:6+rand(i*7+17)*26
        }));
        function pressureWave(x,y,radius,power,dark,time) {
            if(power<=.005)return;
            const core=ctx.createRadialGradient(x,y,0,x,y,radius*.75);
            if(dark){
                core.addColorStop(0,'rgba(255,231,169,'+(.20*power)+')');
                core.addColorStop(.17,'rgba(253,88,18,'+(.21*power)+')');
                core.addColorStop(.60,'rgba(106,16,12,'+(.09*power)+')');
                core.addColorStop(1,'rgba(30,0,0,0)');
            }else{
                core.addColorStop(0,'rgba(237,255,255,'+(.24*power)+')');
                core.addColorStop(.26,'rgba(98,193,255,'+(.18*power)+')');
                core.addColorStop(1,'rgba(0,29,100,0)');
            }
            ctx.globalCompositeOperation='screen';
            ctx.fillStyle=core;
            ctx.fillRect(x-radius,y-radius,radius*2,radius*2);
            ctx.globalCompositeOperation='source-over';
        }
        // Rebuilt from V25's layered incandescent contour, but drawn ONLY
        // on the separate post-WebGL highlights canvas. Background soot
        // can therefore never flatten its brightness.
        function drawV25HotFibers(seconds,progress,fade,w,h){
            const edge=y=>edgeAt(y,seconds,progress,w);
            ctx.save();
            ctx.globalCompositeOperation='lighter';
            ctx.beginPath();
            for(let y=-12,i=0;y<=h+12;y+=4.0,i++){
                if(i===0)ctx.moveTo(edge(y),y);
                else ctx.lineTo(edge(y),y);
            }
            ctx.lineJoin='round';
            ctx.lineCap='round';
            ctx.globalAlpha=.72*fade;
            ctx.shadowColor='#ff2903';
            ctx.shadowBlur=18;
            ctx.strokeStyle='#ff3008';
            ctx.lineWidth=19;
            ctx.stroke();
            ctx.globalAlpha=.83*fade;
            ctx.shadowColor='#ffa620';
            ctx.shadowBlur=12;
            ctx.strokeStyle='#ff9c12';
            ctx.lineWidth=9;
            ctx.stroke();
            ctx.globalAlpha=.89*fade;
            ctx.shadowColor='#ffef83';
            ctx.shadowBlur=8;
            ctx.strokeStyle='#ffdf54';
            ctx.lineWidth=5;
            ctx.stroke();
            ctx.globalAlpha=.93*fade;
            ctx.shadowColor='#fff9dd';
            ctx.shadowBlur=4;
            ctx.strokeStyle='#fffce8';
            ctx.lineWidth=1.9;
            ctx.stroke();
            ctx.shadowBlur=0;

            // V25's incandescent pockets: stretched, flickering vertical
            // tongues without a regular grid or a horizontal glowing band.
            for(let j=0,y=-66;y<h+90;j++,y+=37){
                const oscillation=Math.sin(seconds*7.3+j*2.71);
                const heat=.55+.45*Math.sin(seconds*4.6+j*1.77)**2;
                const xx=edge(y)+12+22*Math.sin(j*1.91+seconds*2.2);
                const sprite=FIRE_GLOW[j%4];
                ctx.globalAlpha=(.21+.28*heat)*fade;
                const rw=62+28*heat,rh=72+24*oscillation;
                ctx.drawImage(sprite,xx-rw*.51,y-rh*.58,
                    rw*1.45,rh*1.62);
            }
            ctx.restore();
        }
        return function drawAtmosphere(seconds,progress,dark,elapsed,cells) {
            const w=innerWidth,h=innerHeight;
            const scale=w<700?.56:.69;
            const bw=Math.max(1,Math.round(w*scale));
            const bh=Math.max(1,Math.round(h*scale));
            if(canvas.width!==bw||canvas.height!==bh){canvas.width=bw;canvas.height=bh;}
            ctx=backCtx;
            ctx.setTransform(scale,0,0,scale,0,0);
            ctx.clearRect(0,0,w,h);
            if(fireCtx){
                if(foreground.width!==bw||foreground.height!==bh){
                    foreground.width=bw;foreground.height=bh;
                }
                fireCtx.setTransform(scale,0,0,scale,0,0);
                fireCtx.clearRect(0,0,w,h);
            }
            const envelope=Math.sin(Math.PI*progress);
            const fade=clamp01(progress/.075)*clamp01((1-progress)/.065);
            advanceCombustion(seconds,progress,dark,elapsed,w,h);
            const sprites=dark?sootSprites:mistSprites;
            // New-world side: red fire trails to the right when burning,
            // blue dawn trails to the left when returning.
            const direction=dark?1:-1;
            // Broken smoke banks with different depths and sizes. The old
            // aligned rows created an artificial horizontal fog ribbon.
            ctx.globalCompositeOperation='source-over';
            const bands=Math.max(8,Math.ceil(h/(dark?116:91)));
            for(let i=0;i<bands;i++){
                const baseY=(i+.15+rand(i*11+39)*.70)*h/bands;
                const y=baseY+31*Math.sin(seconds*1.6+i*1.47);
                const x=edgeAt(y,seconds,progress,w)+direction*
                    (dark?76+rand(i*19+6)*260:120)+
                    Math.sin(seconds*.93+i*1.3)*37;
                const width=dark?170+rand(i*29+12)*220:250;
                const height=dark?165+rand(i*7+5)*170:245;
                ctx.save();
                ctx.globalAlpha=(dark?.34:.21)*fade*(.55+.45*envelope);
                ctx.translate(x,y);
                ctx.rotate(.27*Math.sin(i*2.1+seconds*.9));
                ctx.drawImage(sprites[i%4],-width/2,-height/2,width,height);
                ctx.restore();
            }
            // Independent turbulent billows peel away and rise.
            for(const item of particles){
                const age=((elapsed/item.lifetime+item.phase)%1);
                const baseY=item.height*h;
                const y=baseY-age*(dark?230:128)+(Math.sin(elapsed*2+item.bend)*15);
                if(y< -230||y>h+230)continue;
                const frontier=edgeAt(baseY,seconds,progress,w);
                const x=frontier+direction*(age*(dark?225:135)+
                    30*Math.sin(age*6.3+item.bend));
                const size=(dark?174:145)*item.scale*(.68+age*1.9);
                const opacity=(dark?.43:.26)*Math.sin(Math.PI*age)*fade*
                    (.55+.45*envelope);
                if(opacity<=.005)continue;
                ctx.save();
                ctx.globalAlpha=opacity;
                ctx.translate(x,y);
                ctx.rotate((item.bend-3.14)*.14+age*.85*direction);
                ctx.scale(1.18,.84);
                ctx.drawImage(sprites[item.sprite],-size/2,-size/2,size,size);
                ctx.restore();
            }
            // Residual devastation: coal-black plumes stay pinned to their
            // original burn positions, expanding long after the tear passes.
            // Composited *before* fire, so the hot core cuts through smoke.
            if(dark){
                ctx.save();
                ctx.globalCompositeOperation='source-over';
                for(const p of residualSoot){
                    const age=1-p.remaining/p.life;
                    const opacity=clamp01(age/.14)*
                        Math.pow(1-age,.49)*(.66+.24*Math.sin(p.seed*3)**2)*fade;
                    if(opacity<.009)continue;
                    ctx.save();
                    ctx.globalAlpha=opacity;
                    ctx.translate(p.x,p.y);
                    ctx.rotate(p.spin+age*.33*Math.sin(p.seed));
                    ctx.scale(1.20,.92);
                    const s=p.size*(1+age*.68);
                    ctx.drawImage(sootSprites[p.sprite],-s/2,-s/2,s,s);
                    ctx.restore();
                }
                ctx.restore();
            }else{
                // The inverse is a slow, organic unfurling: broad milky
                // radiance behind the rebuilt sky, not a cold explosion.
                ctx.save();
                ctx.globalCompositeOperation='screen';
                for(let n=0;n<3;n++){
                    const yy=(n+.43)*h/3+Math.sin(seconds*.8+n*2)*30;
                    const xx=edgeAt(yy,seconds,progress,w)-
                        (88+55*Math.sin(n*2.1+seconds*.7));
                    const radius=145+65*Math.sin(seconds*.7+n*1.7)**2;
                    const bloom=ctx.createRadialGradient(xx,yy,8,xx,yy,radius);
                    bloom.addColorStop(0,'rgba(250,255,255,.10)');
                    bloom.addColorStop(.33,'rgba(164,237,255,.07)');
                    bloom.addColorStop(.74,'rgba(117,198,255,.04)');
                    bloom.addColorStop(1,'rgba(117,198,255,0)');
                    ctx.globalAlpha=fade;
                    ctx.fillStyle=bloom;
                    ctx.fillRect(xx-radius,yy-radius,radius*2,radius*2);
                }
                ctx.restore();
            }
            // The impact happens at ignition and again as the rupture reaches
            // the middle of the screen; pulses are intentionally fleeting.
            for(const moment of (dark?[.10,.48]:[])){
                const age=(progress-moment)/.125;
                if(age<0||age>1)continue;
                const intensity=(1-age)*(1-age)*fade;
                // A single-frame-ish exposure bloom punches through
                // the entire page; the tone is red or icy blue by direction.
                ctx.globalCompositeOperation='screen';
                ctx.fillStyle=dark
                    ? 'rgba(255,81,26,'+(.095*intensity)+')'
                    : 'rgba(150,219,255,'+(.080*intensity)+')';
                ctx.fillRect(0,0,w,h);
                ctx.globalCompositeOperation='source-over';
                const x=edgeAt(h*.51,seconds,progress,w);
                const y=h*.51;
                const radius=95+age*Math.max(w,h)*.9;
                pressureWave(x,y,radius,intensity,dark,seconds);
                ctx.globalAlpha=(dark?.20:.28)*intensity;
                ctx.lineWidth=(dark?2.5:2)*Math.max(.4,1-age);
                ctx.strokeStyle=dark?'#ffb36c':'#b5eaff';
                ctx.beginPath();
                for(let i=0;i<=110;i++){
                    const a=i/110*Math.PI*2;
                    const jag=1+.03*Math.sin(a*29+seconds*12)+
                        .05*Math.sin(a*13-seconds*5);
                    const rx=Math.cos(a)*radius*jag,ry=Math.sin(a)*radius*jag;
                    if(i===0)ctx.moveTo(x+rx,y+ry);else ctx.lineTo(x+rx,y+ry);
                }
                ctx.stroke();
                ctx.globalAlpha=1;
                // Only combustion throws straight, fiery projectile trails.
                // Return-to-blue has no streaks or sparks whatsoever.
                if(dark){
                  ctx.globalCompositeOperation='screen';
                  for(const bit of shockDebris){
                    const f=age*(.5+bit.seed*.5);
                    const travel=bit.velocity*f;
                    const px=x+Math.cos(bit.angle)*travel;
                    const py=y+Math.sin(bit.angle)*travel;
                    const vx=Math.cos(bit.angle)*bit.length*(1-age);
                    const vy=Math.sin(bit.angle)*bit.length*(1-age);
                    ctx.globalAlpha=(dark?.82:.68)*intensity*(.3+bit.seed*.7);
                    ctx.strokeStyle=dark?'#ffdd9b':'#e0faff';
                    ctx.lineWidth=.6+bit.seed*1.3;
                    ctx.beginPath();
                    ctx.moveTo(px,py);
                    ctx.lineTo(px-vx,py-vy);
                    ctx.stroke();
                  }
                }
                ctx.globalCompositeOperation='source-over';
                ctx.globalAlpha=1;
            }
            // Real flame tongues break OUT of the burn front into the sky.
            // They are thin, tapered Bezier ribbons with an unstable pulse,
            // rather than round glowing particles or a uniform bright line.
            if(dark){
                ctx.save();
                ctx.globalCompositeOperation='screen';
                const count=Math.ceil(h/11.5);
                for(let j=0;j<count;j++){
                    const seed=rand(j*13+167);
                    const y=(j+seed*.78)*11.5-5;
                    const x=edgeAt(y,seconds,progress,w);
                    if(x < -90 || x > w+90)continue;
                    const ripple=Math.sin(seconds*(3.4+rand(j*11+4)*2.4)+
                        j*2.09+seed*3.1);
                    const heat=clamp01(.58+ripple*.34+
                        .16*Math.sin(j*1.17-seconds*7.1));
                    if(heat<.34)continue;
                    const length=(22+rand(j*23+19)*75)*(.5+heat*.94);
                    const bend=.18+rand(j*17+42)*.66;
                    const tipX=x-length*(.76+.19*seed);
                    const tipY=y-length*bend;
                    const thick=(3.2+rand(j*31+11)*10.3)*(.5+heat);
                    const gradient=ctx.createLinearGradient(x,y,tipX,tipY);
                    gradient.addColorStop(0,'rgba(255,255,242,.99)');
                    gradient.addColorStop(.28,'rgba(255,224,84,.96)');
                    gradient.addColorStop(.59,'rgba(255,76,10,.64)');
                    gradient.addColorStop(1,'rgba(182,17,6,0)');
                    ctx.beginPath();
                    ctx.moveTo(x+2,y+thick*.5);
                    ctx.bezierCurveTo(
                        x-length*.22,y-thick*.25,
                        tipX+length*.36,tipY+thick*.68,tipX,tipY);
                    ctx.bezierCurveTo(
                        tipX+length*.32,tipY-thick*.22,
                        x-length*.17,y-thick*.74,
                        x+2,y-thick*.65);
                    ctx.closePath();
                    ctx.globalAlpha=Math.min(1,heat*1.08)*fade;
                    ctx.fillStyle=gradient;
                    ctx.shadowBlur=0;
                    ctx.fill();
                    if(heat>.66){
                        ctx.globalAlpha=(heat-.54)*1.40*fade;
                        ctx.strokeStyle='#fffce0';ctx.lineWidth=.9+heat*1.1;
                        ctx.beginPath();ctx.moveTo(x,y);
                        ctx.quadraticCurveTo(x-length*.3,y-length*.11,
                            tipX+length*.19,tipY+thick*.18);
                        ctx.stroke();
                    }
                }
                ctx.restore();
            }

            // Carbonized paper has a fine, ragged edge. The charcoal layer
            // persists continuously, but the white-hot core does NOT.
            ctx.save();
            ctx.beginPath();
            for(let y=-12,i=0;y<=h+12;y+=3.6,i++){
                const x=edgeAt(y,seconds,progress,w);
                if(i===0)ctx.moveTo(x,y);else ctx.lineTo(x,y);
            }
            ctx.lineCap='round';ctx.lineJoin='round';
            if(dark){
                ctx.strokeStyle='rgba(9,5,7,.81)';
                ctx.lineWidth=18;ctx.shadowBlur=0;
                ctx.stroke();
                ctx.strokeStyle='rgba(210,45,9,.53)';
                ctx.lineWidth=6;
                ctx.stroke();
            }else{
                ctx.strokeStyle='rgba(27,95,190,.22)';
                ctx.lineWidth=27;ctx.shadowColor='#56bdff';ctx.shadowBlur=40;
                ctx.stroke();
                ctx.strokeStyle='rgba(132,225,255,.51)';
                ctx.lineWidth=11;ctx.shadowColor='#8aeaff';ctx.shadowBlur=30;
                ctx.stroke();
                ctx.strokeStyle='rgba(249,255,255,.65)';
                ctx.lineWidth=2.7;ctx.shadowBlur=11;
                ctx.stroke();
            }
            ctx.restore();
            if(dark){
                // Intermittent ignition cells: varying width/color/intensity
                // make the bright edge resemble burning fibres, not neon.
                ctx.save();
                ctx.globalCompositeOperation='screen';
                ctx.lineCap='round';
                for(let y=-8;y<h+8;y+=5.8){
                    const intensity=clamp01(.58+
                        .29*Math.sin(y*.054+seconds*3.7)+
                        .21*Math.sin(y*.147-seconds*8.9)+
                        .13*Math.sin(y*.337+seconds*16.4));
                    if(intensity<.47)continue;
                    const x=edgeAt(y,seconds,progress,w);
                    const nextX=edgeAt(y+5.8,seconds,progress,w);
                    ctx.globalAlpha=intensity*fade;
                    ctx.lineWidth=1.4+intensity*4.6;
                    ctx.shadowBlur=0;
                    ctx.strokeStyle=intensity>.75?'#fff8d7':
                        intensity>.58?'#ffd369':'#ff831b';
                    ctx.beginPath();ctx.moveTo(x,y);
                    ctx.lineTo(nextX,y+5.8);ctx.stroke();
                }
                ctx.restore();
                // Fragmented ignition on real microscopic perforations.
                // Missing arc sections stop them resembling punched circles.
                ctx.save();
                ctx.globalCompositeOperation='screen';
                ctx.shadowBlur=0;
                for (let i=0; i<cells.length; i++) {
                    const c=cells[i];
                    ctx.globalAlpha=(.42+.34*c.heat)*fade;
                    ctx.strokeStyle=c.heat>.73?'#fff6bf':
                        c.heat>.38?'#ffd166':'#ff621c';
                    ctx.lineWidth=.8+Math.min(2.6,c.radius*.24);
                    const n=c.points.length;
                    ctx.beginPath();
                    for (let j=0;j<n;j++) {
                        if ((j+i*3)%5>2)continue;
                        const a=c.points[j],b=c.points[(j+1)%n];
                        ctx.moveTo(a[0],a[1]);ctx.lineTo(b[0],b[1]);
                    }
                    ctx.stroke();
                }
                ctx.restore();
                // Small carbon flecks stick to the still-blue paper just
                // ahead of the bite; no large rectangular glitch debris.
                ctx.save();
                for(let j=0;j<Math.ceil(h/10);j++){
                    const y=(j+rand(j*5+61)*.8)*10;
                    const x=edgeAt(y,seconds,progress,w)-
                        (5+rand(j*17+38)*24);
                    const size=.5+rand(j*29+11)*2.5;
                    const visible=.25+.59*rand(j*13+7);
                    ctx.globalAlpha=visible*fade;
                    ctx.fillStyle='#150b0a';
                    ctx.beginPath();
                    ctx.ellipse(x,y,size*.71,size,rand(j*7+31)*3.14,
                        0,Math.PI*2);
                    ctx.fill();
                }
                ctx.restore();
            }
            // COMPOSITING BARRIER: smoky background, curled tongues and
            // charcoal seam are now COMPLETELY behind the WebGL fire wall.
            // The upper layer contains additive V25 incandescent wake and
            // embers only. No opaque smoke can obscure the white-hot core.
            if(fireCtx){
                ctx=fireCtx;
                if(dark)drawV25HotFibers(seconds,progress,fade,w,h);
            }
            // The key property V3-V6 lost: particles remain at their
            // birth position while the front advances. A wide, incandescent
            // WAKE builds behind the tearing page instead of following
            // it as one thin, plastic-looking stripe.
            ctx.save();
            ctx.globalCompositeOperation='lighter';
            for(const p of combustion){
                if(p.kind==='ash'||p.kind==='leaf'||p.kind==='pollen')continue;
                const age=1-p.remaining/p.life;
                const opacity=clamp01(p.remaining/.22)*
                    clamp01(age/.08)*(1-age*.30)*
                    (p.kind==='ember'?.93:p.kind==='glow'?.13:.62)*fade*
                    (dark?Math.exp(-Math.max(0,p.x-
                        edgeAt(p.y,seconds,progress,w))/
                        (p.kind==='ember'?475:145)):1);
                if(opacity<.012)continue;
                ctx.save();
                ctx.globalAlpha=opacity;
                ctx.translate(p.x,p.y);
                ctx.rotate(p.angle+Math.sin(elapsed*4+p.seed)*.13);
                const large=p.kind==='flame';
                const sx=p.radius*(p.kind==='glow'?1.7:large?.96:1.32)*(1+age*.32);
                const sy=p.radius*(p.kind==='glow'?1.4:large?1.78:1.35)*(1+age*.57);
                const sprite=p.kind==='flame'?FIRE_GLOW[p.sprite]:
                    p.kind==='glow'?BLUE_GLOW[p.sprite]:EMBER_GLOW;
                ctx.drawImage(sprite,-sx,-sy,sx*2,sy*2);
                ctx.restore();
            }
            ctx.restore();
            // Rebirth uses soft, rotating, organic leaf/petal silhouettes,
            // minute circular pollen and spacious white-blue bokeh. No
            // rectangular ions, no warm textures and NO glowing streaks.
            if(!dark){
                ctx.save();
                ctx.globalCompositeOperation='screen';
                for(const p of combustion){
                    if(p.kind!=='leaf'&&p.kind!=='pollen')continue;
                    const age=1-p.remaining/p.life;
                    const opacity=clamp01(age/.17)*clamp01(p.remaining/.55)*
                        (p.kind==='leaf'?.47:.28)*fade;
                    if(opacity<.012)continue;
                    ctx.save();
                    ctx.globalAlpha=opacity;
                    ctx.translate(p.x+11*Math.sin(elapsed*1.6+p.seed),p.y);
                    ctx.rotate(p.angle+age*1.65*Math.sin(p.seed*2.5));
                    if(p.kind==='leaf'){
                        const r=p.radius;
                        ctx.shadowBlur=13;
                        ctx.shadowColor='#bbf4ff';
                        ctx.fillStyle=p.sprite%2?'#e6ffff':'#ffffff';
                        ctx.beginPath();
                        ctx.moveTo(0,-r*1.65);
                        ctx.bezierCurveTo(r*.97,-r*.48,r*.85,r*.60,0,r*1.35);
                        ctx.bezierCurveTo(-r*.92,r*.28,-r*.94,-r*.57,0,-r*1.65);
                        ctx.fill();
                        ctx.globalAlpha=opacity*.38;
                        ctx.strokeStyle='#70c9ea';
                        ctx.lineWidth=.65;
                        ctx.beginPath();ctx.moveTo(0,-r*1.15);
                        ctx.quadraticCurveTo(-r*.17,0,0,r*.95);ctx.stroke();
                    }else{
                        const r=p.radius;
                        const halo=ctx.createRadialGradient(0,0,0,0,0,r*3);
                        halo.addColorStop(0,'rgba(255,255,255,.78)');
                        halo.addColorStop(.25,'rgba(225,250,255,.40)');
                        halo.addColorStop(1,'rgba(150,215,255,0)');
                        ctx.fillStyle=halo;
                        ctx.beginPath();ctx.arc(0,0,r*3,0,Math.PI*2);ctx.fill();
                    }
                    ctx.restore();
                }
                ctx.restore();
            }
            // Minute black flecks, never rectangular shards on the blue side.
            ctx.save();
            ctx.globalCompositeOperation='source-over';
            for(const p of combustion){
                if(p.kind!=='ash')continue;
                ctx.globalAlpha=clamp01(p.remaining/.25)*.7*fade;
                ctx.fillStyle='#190d10';
                ctx.save();ctx.translate(p.x,p.y);ctx.rotate(elapsed*2+p.angle);
                ctx.fillRect(-p.radius*.5,-p.radius*.5,p.radius,p.radius*1.8);
                ctx.restore();
            }
            ctx.restore();
            // Irregular burnt page sections tumble away and reveal their
            // blackened underside, with an occasional incandescent rim.
            if(dark){
                ctx.save();
                ctx.globalCompositeOperation='source-over';
                for(const p of tornPaper){
                    const age=1-p.remaining/p.life;
                    const opacity=clamp01(age/.08)*clamp01(p.remaining/.4)*fade;
                    if(opacity<.01)continue;
                    ctx.save();
                    ctx.globalAlpha=opacity;
                    ctx.translate(p.x,p.y);
                    ctx.rotate(p.angle);
                    ctx.beginPath();
                    p.outline.forEach((v,i)=>{
                        const px=Math.cos(v.a)*v.r*p.radius;
                        const py=Math.sin(v.a)*v.r*p.radius*.74;
                        if(i===0)ctx.moveTo(px,py);else ctx.lineTo(px,py);
                    });
                    ctx.closePath();
                    // Distinct silhouette first: some fragments are almost
                    // pitch black against the blazing furnace.
                    ctx.shadowBlur=7;
                    ctx.shadowColor=age<.40?'#ff5d1b':'#0b0407';
                    ctx.fillStyle=p.seed>3?'#080408':'#241014';
                    ctx.fill();
                    ctx.shadowBlur=0;
                    // Only discontinuous edges glow: a complete neon
                    // polygon outline looks like a sci-fi icon, not char.
                    ctx.lineWidth=.70+Math.sin(p.seed)**2*.95;
                    ctx.strokeStyle=age<.50?'rgba(255,112,34,.82)':
                        'rgba(125,32,16,.31)';
                    ctx.beginPath();
                    for(let i=0;i<p.outline.length;i++){
                        if((i+Math.floor(p.seed*7))%4>1)continue;
                        const a=p.outline[i];
                        const b=p.outline[(i+1)%p.outline.length];
                        ctx.moveTo(Math.cos(a.a)*a.r*p.radius,
                            Math.sin(a.a)*a.r*p.radius*.74);
                        ctx.lineTo(Math.cos(b.a)*b.r*p.radius,
                            Math.sin(b.a)*b.r*p.radius*.74);
                    }
                    ctx.stroke();
                    // Cracks are molten for the first half of the flight.
                    if(age<.55){
                        ctx.globalCompositeOperation='lighter';
                        ctx.shadowBlur=6;
                        ctx.shadowColor='#ff5e0a';
                        ctx.strokeStyle=age<.22?'#ffe9a2':'#ff761e';
                        ctx.lineWidth=.60+(.55-age)*1.4;
                        ctx.globalAlpha=opacity*(1-age);
                        ctx.beginPath();
                        ctx.moveTo(-p.radius*.48,-p.radius*.06);
                        ctx.lineTo(-p.radius*.08,p.radius*.14);
                        ctx.lineTo(p.radius*.27,-p.radius*.22);
                        ctx.stroke();
                        ctx.shadowBlur=0;
                        ctx.globalCompositeOperation='source-over';
                        ctx.globalAlpha=opacity;
                    }
                    // Thin blue-white unburnt fibers still visible on a
                    // few ripped faces, before the back chars completely.
                    if(p.seed>4.5&&age<.52){
                        ctx.globalAlpha*=.45*(1-age);
                        ctx.strokeStyle='#c5e7f7';
                        ctx.beginPath();
                        ctx.moveTo(-p.radius*.42,-p.radius*.16);
                        ctx.quadraticCurveTo(0,p.radius*.25,p.radius*.28,0);
                        ctx.stroke();
                    }
                    ctx.restore();
                }
                ctx.restore();
            }
            // Sharp, directional embers / crystalline fragments, not blobs.
            if(dark){ctx.save();
            ctx.globalCompositeOperation='screen';
            for(const mote of motes){
                const age=(elapsed*.74+mote.phase)%1;
                const yy=mote.y*h-age*mote.speed+Math.sin(age*12+mote.phase*8)*9;
                const x=edgeAt(yy,seconds,progress,w)+direction*age*mote.drift;
                if(x<-25||x>w+25||yy<-25||yy>h+25)continue;
                const opacity=(1-age)*fade*.98;
                ctx.globalAlpha=opacity;
                ctx.shadowColor='#ff8c28';
                ctx.shadowBlur=5;
                ctx.strokeStyle=age<.37?'#fff2a1':'#ff922d';
                ctx.lineWidth=1.0+(.5-age)*.7;
                ctx.beginPath();
                ctx.moveTo(x,yy);
                ctx.lineTo(x-direction*mote.length*.4,yy+mote.length);
                ctx.stroke();
            }
            ctx.shadowBlur=0;
            ctx.restore();}
        };
    }

    let atmosphereWarmPromise=null;
    function prewarmAtmosphere() {
        if(atmosphereWarmPromise)return atmosphereWarmPromise;
        atmosphereWarmPromise=new Promise(resolve=>{
            const scratchCanvas=document.createElement('canvas');
            function step(){
                if(atmosphereAssetCache?.EMBER_GLOW){resolve();return;}
                // Exactly one texture per task: no more 270ms blocking call.
                createAtmosphere(scratchCanvas,true);
                if(atmosphereAssetCache?.EMBER_GLOW){resolve();return;}
                setTimeout(step,24);
            }
            setTimeout(step,40);
        });
        return atmosphereWarmPromise;
    }

    let atmosphereEdge=null;
    function edgeAt(y,seconds,progress,width){
        return atmosphereEdge
            ? atmosphereEdge(y)
            : makeEdge(progress,seconds,Boolean(window.__kkptVisualDark),width)(y);
    }

    // Original V2's moving flame sprites and three bright contours, rebuilt
    // with bounded particle counts. No WebGL, no full-screen noise pass,
    // no 1,000-point polygon or per-frame image-texture upload.
    let sprites=null;
    function makeSprites() {
        if (sprites) return sprites;
        function radial(stops) {
            const el=document.createElement('canvas');
            el.width=el.height=96;
            const c=el.getContext('2d');
            const g=c.createRadialGradient(48,48,0,48,48,48);
            stops.forEach(pair=>g.addColorStop(pair[0],pair[1]));
            c.fillStyle=g;c.fillRect(0,0,96,96);
            return el;
        }
        sprites={
            flame:radial([[0,'#fffbed'],[.18,'#fff2a0'],
                [.43,'#ffb42b'],[.70,'#ff360088'],[1,'#8f050000']]),
            ember:radial([[0,'#ffffff'],[.15,'#fff6a8'],
                [.44,'#ff9900cc'],[1,'#ef280000']]),
            smoke:radial([[0,'#080608dd'],[.30,'#100b10bb'],
                [.62,'#160f1677'],[1,'#08050800']]),
            sky:radial([[0,'#ffffff'],[.16,'#e6ffff'],
                [.46,'#94deffe0'],[1,'#4ab5ff00']]),
            mist:radial([[0,'#f2fdffb0'],[.4,'#abdffff0'],
                [1,'#a9e7ff00']])
        };
        return sprites;
    }

    // V30 fracture edge. Multi-scale piecewise-linear angular ridges have
    // HARD corners; the old three sinusoidal waves were far too smooth.
    function edgeShard(q,seed){
        const i=Math.floor(q),f=q-i;
        const a=Math.sin(i*2.41+seed);
        return a+(Math.sin((i+1)*2.41+seed)-a)*f;
    }
    function makeEdge(t,seconds,dark,w) {
        const wave=Math.sin(Math.PI*t);
        const center=dark?w+105-(w+210)*smooth(t)
            :-105+(w+210)*smooth(t);
        return y=>center+wave*(
            10*Math.sin(y*.023+seconds*5.5)+
             5*Math.sin(y*.071-seconds*8.4)+
             3*Math.sin(y*.14+seconds*12)+
            12*edgeShard(y/32+seconds*.48,1.73)+
             6*edgeShard(y/10-seconds*1.2,4.19));
    }

    // Clip the ACTUAL preloaded Wiki frame, precisely where the fire is.
    function clipFrame(edge) {
        const w=innerWidth,h=innerHeight;
        const rows=Math.max(128,Math.ceil(h/6));
        const pts=[];
        for(let i=rows;i>=0;i--) {
            const y=h*i/rows;
            pts.push(edge(y).toFixed(1)+'px '+y.toFixed(1)+'px');
        }
        frame.style.clipPath=clipSide==='right'
            ? 'polygon(100% 0,100% 100%,'+pts.join(',')+')'
            : 'polygon(0 0,0 100%,'+pts.join(',')+')';
    }

    // ================================================================
    // V30: three compositing planes:
    // smoke/tongues BEHIND, genuine WebGL2 incandescent furnace, then
    // additive V25 hot fibers and embers IN FRONT. Never soot over flame.
    // ================================================================
    function createWebGLCurtain(dark) {
        if(!window.WebGL2RenderingContext)return null;
        const surface=document.createElement('canvas');
        surface.id='kkpt-webgl';
        surface.setAttribute('aria-hidden','true');
        surface.style.cssText='position:fixed;inset:0;width:100vw;'+
            'height:100vh;z-index:2147482100;pointer-events:none;'+
            'display:block;background:transparent';
        document.body.appendChild(surface);
        let gl=null;
        let curtain=null,sparks=null,plumes=null;
        let attachedAtmosphere=null;
        let raf=0,disposed=false,contextLost=false;
        const mobile=innerWidth<700||
            matchMedia('(pointer:coarse)').matches;
        const view=[innerWidth,innerHeight];
        const sharedFns=`
            precision highp float;
            float hash(vec2 p) {
                p=fract(p*vec2(.3183099,.3678794)+.13787);
                p*=17.0;
                return fract(p.x*p.y*(p.x+p.y));
            }
            float noise2(vec2 p) {
                vec2 i=floor(p),f=fract(p);
                f=f*f*(3.0-2.0*f);
                return mix(mix(hash(i),hash(i+vec2(1.0,0.0)),f.x),
                           mix(hash(i+vec2(0.0,1.0)),hash(i+1.0),f.x),f.y);
            }
            float fbm(vec2 p) {
                float n=0.0,a=.56;
                for(int j=0;j<3;j++){
                    n+=a*noise2(p);
                    p=mat2(1.61,-1.13,1.13,1.61)*p+13.31;
                    a*=.50;
                }
                return n;
            }
            float smooth01(float p){return p*p*(3.0-2.0*p);}
            float angular(float q,float seed){
                float i=floor(q),f=fract(q);
                float a=sin(i*2.41+seed);
                return mix(a,sin((i+1.0)*2.41+seed),f);
            }
            float stormEdge(float y,float t,float clock,float w,float dark) {
                float s=smooth01(t);
                float center=mix(-105.0+(w+210.0)*s,
                                  w+105.0-(w+210.0)*s,dark);
                float wobble=sin(3.14159265*t);
                return center+wobble*(
                    10.0*sin(y*.023+clock*5.5)+
                     5.0*sin(y*.071-clock*8.4)+
                     3.0*sin(y*.14+clock*12.0)+
                    12.0*angular(y/32.0+clock*.48,1.73)+
                     6.0*angular(y/10.0-clock*1.2,4.19));
            }
        `;
        const backgroundVert=`#version 300 es
            out vec2 vUV;
            void main(){
                vec2 p=vec2(gl_VertexID==1?3.0:-1.0,
                            gl_VertexID==2?3.0:-1.0);
                vUV=(p+1.0)*.5;
                gl_Position=vec4(p,0.0,1.0);
            }`;
        const backgroundFrag=`#version 300 es
        precision highp float;
            in vec2 vUV;
            out vec4 outColor;

        uniform vec2 uView;

        uniform float uClock;
        uniform float uProgress;
        uniform float uDark;

        float random2(vec2 p) {
            return fract(sin(dot(p, vec2(127.1,311.7))) * 43758.5453123);
        }
        float noise(vec2 p) {
            vec2 i = floor(p), f = fract(p);
            vec2 u = f*f*(3.0-2.0*f);
            return mix(mix(random2(i),random2(i+vec2(1.0,0.0)),u.x),
                       mix(random2(i+vec2(0.0,1.0)),random2(i+1.0),u.x),u.y);
        }
        float fbm(vec2 p) {
            float result = 0.0, amp = 0.5;
            for (int i = 0; i < 5; i++) {
                result += amp * noise(p);
                p = mat2(1.6,-1.2,1.2,1.6) * p;
                amp *= 0.5;
            }
            return result;
        }
        float smoothProgress(float t) { return t*t*(3.0-2.0*t); }
        float edge(float y) {
            float w = uView.x;
            float wave=sin(3.14159265*uProgress);
            float yn=y/uView.y;
            float lobes=.63*sin(yn*9.3+uClock*.38+.4)+
                .27*sin(yn*22.7-uClock*.28+1.4)+
                .10*sin(yn*51.1+uClock*.58);
            float localProgress=uDark>.5
                ? clamp(uProgress+.285*wave*lobes,0.0,1.0)
                : uProgress;
            float t = smoothProgress(localProgress);
            float c = uDark > .5 ? w+110.0-(w+220.0)*t : -110.0+(w+220.0)*t;
            float turbulent=uDark>.5
                ? 22.0*sin(y*.019+uClock*1.8)+
                  13.0*sin(y*.061-uClock*3.6)+
                   6.0*sin(y*.135+uClock*7.9)+
                   17.0*(abs(sin(y*.133+uClock*3.7+
                       .8*sin(y*.043-uClock*1.1)))-.5)+
                   5.0*sin(y*.325-uClock*10.8)+
                   2.5*sin(y*.74+uClock*16.2)+
                   3.4*sin(y*.51-uClock*13.3)+
                   1.8*sin(y*.94+uClock*21.1)
                : 28.0*sin(y*.012+uClock*3.1)+
                  17.0*sin(y*.041-uClock*5.7)+
                   7.0*sin(y*.10+uClock*10.0);
            return c+wave*turbulent;
        }
        void main() {
            vec2 p = vec2(vUV.x*uView.x,(1.0-vUV.y)*uView.y);
            float d = p.x-edge(p.y);
            // Entire sky/background pixels outside the active burn wake
            // need no fbm work at all; this saves most pixels early/late.
            if ((uDark > .5 && (d < -138.0 || d > 970.0)) ||
                (uDark < .5 && (d > 148.0 || d < -1050.0))) {
                outColor = vec4(0.0);
                return;
            }
            float oldSide = uDark > .5 ? -d : d;
            float t = uClock;
            float impact = sin(3.14159265*uProgress);
            vec3 col = vec3(0.0);
            float alpha = 0.0;

            if (uDark > .5) {
                // V7: intact sky remains clean on the OLD side.
                // Incandescent wake + char exist ONLY on the newly
                // revealed Kuronata side, trailing the traveling tear.
                float wakeSide = -oldSide;
                vec2 sq = vec2(p.y*.007-t*.29,wakeSide*.006+t*.12);
                vec2 warp = vec2(fbm(sq*1.5+vec2(t*.13,0.0)),
                                 fbm(sq*1.9+vec2(0.0,-t*.21)));
                float smokeCloud = fbm(sq*2.0+warp*2.2);
                float smokeDetail = fbm(sq*5.1-warp*.8);
                float billow = smoothstep(.29,.69,smokeCloud*.88+smokeDetail*.34);
                float soot = smoothstep(-42.0,24.0,wakeSide)*
                    (1.0-smoothstep(390.0,850.0,wakeSide))*
                    (.47+.53*billow);
                vec3 sootColor = mix(vec3(.010,.009,.012),vec3(.066,.019,.018),smokeCloud);

                // Flame remains close to the paper boundary; the far wake
                // retains soot and charcoal, not wandering bright blobs.
                vec2 q = vec2(p.y*.015-t*.66,wakeSide*.012-t*.49);
                float turbulence = fbm(q+vec2(fbm(q*1.6)*2.7,-t*.25));
                float shredded = fbm(q*3.9+vec2(t*.25,-t*.32));
                float lengthOfTongue = 57.0+65.0*turbulence+33.0*shredded;
                float raggedEdge = 1.0-smoothstep(lengthOfTongue-35.0,lengthOfTongue+18.0,wakeSide);
                float flame = raggedEdge*smoothstep(-65.0,23.0,wakeSide)*
                    smoothstep(.17,.65,turbulence+.38*shredded);
                float ignitionNoise=fbm(vec2(p.y*.057+t*.19,
                    t*.84+sin(p.y*.029)*.44));
                float ignite=.33+.67*smoothstep(.25,.59,
                    ignitionNoise+.13*sin(p.y*.092-t*7.8));
                // Burning paper has three distinct temperatures: dark red
                // carbon, yellow incandescent fibers and discontinuous
                // white-hot ignition at the freshly eroded edge.
                float crackle = noise(vec2(p.y*.19-t*1.7,
                    sin(p.y*.12+t*2.4)*1.4+t*2.3));
                float brightGaps = smoothstep(.24,.65,
                    ignitionNoise*.78+crackle*.54);
                float core = exp(-abs(d)/6.8)*(.44+.56*brightGaps);
                float whiteCore = exp(-pow(d/4.2,2.0)) *
                    (.18+.82*brightGaps);
                float outer = exp(-abs(d)/28.0)*(.32+.68*ignite);
                float heat = clamp(flame*.98+core*.97,0.0,1.0);
                float hotPockets = smoothstep(.43,.73,turbulence*.78+shredded*.55)*
                    exp(-max(0.0,wakeSide)/62.0);
                vec3 fireColor = mix(vec3(.40,.012,.005),vec3(1.0,.18,.007),
                    smoothstep(.07,.51,heat));
                fireColor = mix(fireColor,vec3(1.0,.72,.075),
                    clamp(flame*.42+core*.82+hotPockets*.55,0.0,.97));
                fireColor = mix(fireColor,vec3(1.0,.995,.86),
                    clamp(whiteCore*1.10+hotPockets*.22,0.0,.96));
                col = mix(sootColor,fireColor,
                    clamp(flame*.93+core*1.22+whiteCore*.58,0.0,1.0));
                alpha = clamp(soot*.67+flame*.92+outer*.28+
                    core*.79+whiteCore*.38,0.0,.98);

                // Sharp micron-scale cinders; the real ember trails live
                // on the separate high-resolution atmosphere canvas.
                vec2 cell = floor((p+vec2(t*23.0,-t*122.0))/11.0);
                vec2 uv = fract((p+vec2(t*23.0,-t*122.0))/11.0)-.5;
                float sparks = (1.0-smoothstep(.015,.12,length(uv)))*
                    step(.991,random2(cell))*exp(-max(0.0,wakeSide)/380.0);
                col = mix(col,vec3(1.0,.78,.23),sparks);
                alpha = max(alpha,sparks*.97);
            } else {
                // Dawn is a living, spreading atmosphere: diffuse cloud,
                // breathing alabaster light and soft shafts. NO electric
                // arcs, ignition lines, flame-shaped sparks or embers.
                float newlyBlue = -oldSide;
                vec2 q = vec2(p.y*.007-t*.16,newlyBlue*.008+t*.10);
                float cloud = fbm(q+vec2(fbm(q*1.6)*1.7,-t*.13));
                float billow = fbm(q*2.9+vec2(t*.08,-t*.11));
                float erosion = smoothstep(.22,.72,cloud*.76+billow*.37);
                float settling = smoothstep(-68.0,35.0,newlyBlue)*
                    exp(-max(0.0,newlyBlue)/440.0);
                float pearlyMist = settling*(.33+.64*erosion);
                float halo = exp(-pow(d/78.0,2.0));
                float innerLight = exp(-pow(d/21.0,2.0));
                float shaftDrift=20.0*sin(p.y*.013-t*1.0)+
                    9.0*sin(p.y*.039+t*.61);
                float softRay=exp(-pow((d+shaftDrift+88.0)/81.0,2.0))*
                    (.32+.68*smoothstep(.28,.81,cloud));
                col=mix(vec3(.075,.30,.57),vec3(.72,.94,1.0),clamp(cloud*.76+.38,0.0,1.0));
                col=mix(col,vec3(.94,.995,1.0),
                    clamp(innerLight*.49+softRay*.20,0.0,.6));
                alpha=clamp(pearlyMist*.42+halo*.30+innerLight*.22+
                    softRay*.14,0.0,.59);
            }

            if(uDark < .5) {
                col = mix(vec3(.065,.21,.35),col,.45);
                alpha = min(alpha*.52,.35);
            }

            // No long-lasting screen tint after the burn has finished.
            alpha *= (.35+.65*impact) * smoothstep(0.0,.07,uProgress) *
                (1.0-smoothstep(.94,1.0,uProgress));
            outColor = vec4(col,alpha);
        }
    `;
        // Main GPU furnace: domain-warped flame bodies, torn contours and
        // extremely hot, irregular interiors. Separate from 2D glow sprites.
        // Flame body extends 20–26% of the full viewport into the dark
        // world, with torn white-hot cells, black voids and rolling soot.
        // Coordinates are in CSS pixels, so low-resolution mobile rendering
        // does not shrink the apparent width of the conflagration.
        const dominantFireFrag=`#version 300 es
            precision highp float;
            in vec2 vUV;
            out vec4 outColor;
            uniform vec2 uView;
            uniform float uClock,uProgress,uDark;

            float h2(vec2 p){
                return fract(sin(dot(p,vec2(127.1,311.7)))*43758.5453123);
            }
            float n2(vec2 p){
                vec2 i=floor(p),f=fract(p);
                f=f*f*(3.0-2.0*f);
                float a=mix(h2(i),h2(i+vec2(1.0,0.0)),f.x);
                float b=mix(h2(i+vec2(0.0,1.0)),h2(i+1.0),f.x);
                return mix(a,b,f.y);
            }
            float f4(vec2 p){
                float v=0.0,a=.5;
                for(int i=0;i<4;i++){
                    v+=a*n2(p);
                    p=mat2(1.61,-1.14,1.14,1.61)*p+7.4;
                    a*=.5;
                }
                return v;
            }
            float sm(float t){return t*t*(3.0-2.0*t);}
            float angular(float q,float seed){
                float i=floor(q),f=fract(q);
                float a=sin(i*2.41+seed);
                return mix(a,sin((i+1.0)*2.41+seed),f);
            }

            // Mirror the native page's clip-path: the flame actually
            // consumes the arriving wiki instead of floating above it.
            float front(float y){
                float wave=sin(3.14159265*uProgress);
                float c=uDark>.5
                    ?uView.x+105.0-(uView.x+210.0)*sm(uProgress)
                    :-105.0+(uView.x+210.0)*sm(uProgress);
                return c+wave*(10.0*sin(y*.023+uClock*5.5)+
                     5.0*sin(y*.071-uClock*8.4)+
                     3.0*sin(y*.14+uClock*12.0)+
                    12.0*angular(y/32.0+uClock*.48,1.73)+
                     6.0*angular(y/10.0-uClock*1.2,4.19));
            }

            void main(){
                vec2 p=vec2(vUV.x*uView.x,(1.0-vUV.y)*uView.y);
                float d=p.x-front(p.y);
                float phase=sin(3.14159265*clamp(uProgress,0.0,1.0));
                float appear=smoothstep(.005,.075,uProgress)*
                    (1.0-smoothstep(.945,1.0,uProgress));
                if(uDark<.5){
                    // Return to Kuranoka is blue haze, not a white screen.
                    float inward=-d;
                    if(inward< -85.0 || inward>660.0){
                        outColor=vec4(0.0);return;
                    }
                    float cloud=f4(vec2(p.y*.010-uClock*.18,
                        inward*.008+uClock*.11));
                    float haze=exp(-max(inward,0.0)/270.0)*
                        smoothstep(-74.0,25.0,inward);
                    float glimmer=exp(-pow(d/46.0,2.0));
                    vec3 col=mix(vec3(.075,.25,.42),
                        vec3(.48,.78,.94),clamp(cloud*.9,0.0,1.0));
                    float alpha=min(.28,haze*(.10+.16*cloud)+glimmer*.13);
                    outColor=vec4(col,alpha*appear);
                    return;
                }

                float span=clamp(uView.x*.225,175.0,475.0);
                if(d < -75.0 || d > span+800.0){
                    outColor=vec4(0.0);return;
                }
                float trail=max(0.0,d);
                // Three differently drifting, vertically anisotropic
                // fields make large flames ROLL upward rather than form
                // V27's orange horizontal bars.
                float wind=sin(p.y*.009+uClock*.61)*13.0+
                    sin(p.y*.027-uClock*1.17)*6.5;
                // Fire flows vertically. High spatial frequency across X,
                // lower frequency along Y: elongated rising structures,
                // not the old horizontal bands.
                float back=f4(vec2(trail*.015-uClock*.15,
                    p.y*.006-uClock*.23));
                float twist=f4(vec2((trail+wind)*.021-uClock*.39+
                    back*1.7,p.y*.013-uClock*.91));
                float tongues=f4(vec2((trail+wind+twist*41.0)*.032,
                    p.y*.010-uClock*1.26+back*.8));
                float cells=f4(vec2((trail+wind)*.053+twist*.72,
                    p.y*.024-uClock*1.95));
                float ragged=f4(vec2((trail+wind)*.075-uClock*.79,
                    p.y*.034-uClock*1.22));

                // Several layers of upward-advecting ignition pockets.
                // Their 2-D centers create *vertical flame lobes* and
                // bright internal cavities, never uniform horizontal bars.
                vec2 fireGrid=vec2(trail/83.0,
                    p.y/113.0+uClock*1.12);
                vec2 fireCell=floor(fireGrid);
                float cellGlow=0.0,cellGold=0.0,cellWhite=0.0;
                float erode=(f4(vec2(p.x*.037-uClock*.26,
                    p.y*.023-uClock*1.8))-.5)*.21;
                for(int cy=-1;cy<=1;cy++){
                    for(int cx=-1;cx<=1;cx++){
                        vec2 c=fireCell+vec2(float(cx),float(cy));
                        float seed=h2(c+vec2(6.4,13.2));
                        float gate=smoothstep(.12,.36,seed);
                        vec2 origin=c+vec2(.18+.64*h2(c+1.6),
                            .12+.76*h2(c+7.3));
                        vec2 delta=fireGrid-origin;
                        delta.x+=.21*sin(delta.y*3.4+uClock*2.8+
                            seed*6.28);
                        float metric=length(delta*vec2(
                            1.15-.16*seed,.69+.23*seed));
                        float localErode=erode*1.55+
                            .045*sin(seed*9.5);
                        float halo=1.0-smoothstep(.25,1.13,metric+localErode);
                        float gold=1.0-smoothstep(.13,.75,metric+localErode);
                        float whiteCore=1.0-smoothstep(.065,.43,
                            metric+localErode);
                        cellGlow=max(cellGlow,halo*gate);
                        cellGold=max(cellGold,gold*gate);
                        cellWhite=max(cellWhite,whiteCore*gate);
                    }
                }

                // The flame front has a contiguous furnace base. Further
                // into the black world, it tears into disjointed billows,
                // white cores, deep red chasms and hanging tongues.
                float field=.44*tongues+.32*twist+.24*cells+
                    .11*sin(p.y*.021-uClock*3.7+trail*.017);
                // Irregular fracture contour: high-frequency noise shears
                // edges into claw-like tongues. Narrow 10px thresholds
                // preserve jagged silhouettes rather than blurred ellipses.
                float tearing=f4(vec2(
                    trail*.024-uClock*.47+twist*.79,
                    p.y*.037-uClock*1.34+back*.39));
                float fiber=f4(vec2(
                    trail*.064+tearing*.7-uClock*.95,
                    p.y*.052-uClock*2.1));
                float edgeReach=span*(.39+.64*back+.42*twist)+
                    (tearing-.49)*92.0+(fiber-.50)*45.0;
                float fadeWidth=1.0-smoothstep(-19.0,19.0,
                    trail-edgeReach);
                float dense=smoothstep(.27,.55,
                    field+ragged*.16+(fiber-.5)*.18);
                float base=exp(-trail/25.0)*
                    (.15+.39*f4(vec2(p.x*.053-uClock*.6,
                        p.y*.021-uClock*.95)));
                // Dense, continuous furnace at the bite, branching into
                // separate caverns in the far wake.
                float body=clamp(max(base,dense)*fadeWidth,0.0,1.0);
                float gaps=smoothstep(.29,.57,
                    cells*.57+ragged*.35+fiber*.15);
                body*=mix(.50,1.0,gaps);

                float incandescent=smoothstep(.38,.61,
                    field+.18*tongues+.10*tearing+
                    .055*sin(p.y*.045-uClock*4.7));
                float yellow=smoothstep(.43,.68,
                    field+.18*cells+.11*base);
                float white=smoothstep(.57,.83,
                    field+.17*cells+.12*incandescent+.06*base);
                float luminous=clamp(body*(.42+.62*incandescent),0.0,1.0);
                // Larger WHITE hot pockets, not uniformly neon orange.
                float hot=body*white*fadeWidth;
                float lip=clamp((1.0-smoothstep(span*.57,span*1.12,
                    trail))*smoothstep(-17.0,14.0,d),0.0,1.0);
                float burnMask=smoothstep(-17.0,13.0,d);
                float near=exp(-abs(d)/12.0);
                float whiteRim=exp(-pow(d/4.5,2.0))*(.75+.25*ragged);

                float smoke=f4(vec2(p.y*.006-uClock*.14+back*1.9,
                    trail*.004-uClock*.10));
                float smokeFine=f4(vec2(p.y*.019-uClock*.33,
                    trail*.012+smoke));
                float shroud=smoothstep(.28,.66,smoke*.72+smokeFine*.34)*
                    (1.0-smoothstep(span+190.0,span+790.0,trail));
                shroud*=smoothstep(-12.0,55.0,d);
                vec3 coal=mix(vec3(.013,.004,.011),
                    vec3(.13,.013,.017),smoke);
                coal+=vec3(.13,.010,.007)*
                    exp(-trail/(span*.93))*(.4+.6*back);
                vec3 col=coal;
                col=mix(col,vec3(.48,.022,.004),clamp(body*.95,0.0,1.0));
                col=mix(col,vec3(1.0,.19,.003),luminous*.92);
                col=mix(col,vec3(1.0,.70,.035),
                    clamp(body*yellow*.72,0.0,1.0));
                col=mix(col,vec3(1.0,.23,.006),
                    clamp(cellGlow*.90*lip,0.0,1.0));
                col=mix(col,vec3(1.0,.78,.045),
                    clamp(cellGold*.98*lip,0.0,1.0));
                col=mix(col,vec3(1.0,.99,.82),
                    clamp(hot*.15+cellWhite*1.01*lip+
                        whiteRim*.86,0.0,1.0));
                col+=vec3(.15,.034,.0)*near;

                float alpha=clamp(shroud*.27*(1.0-body*.83)*burnMask+
                    body*.91*burnMask+cellGlow*.86*lip+
                    near*.68+whiteRim*.32,0.0,.99);
                // Remove flat horizontal slabs leaking into the old sky.
                col=mix(vec3(.36,.025,.006),col,
                    max(burnMask,whiteRim));
                // Side sparks, biased into the charred world. The richer
                // flying particles remain in the V13 atmosphere layer.
                vec2 moteCell=floor(vec2(p.x+uClock*24.0,
                    p.y+uClock*139.0)/17.0);
                vec2 moteUv=fract(vec2(p.x+uClock*24.0,
                    p.y+uClock*139.0)/17.0)-.5;
                float mote=(1.0-smoothstep(.04,.16,length(moteUv)))*
                    step(.989,h2(moteCell))*
                    exp(-trail/(span*1.4))*step(0.0,d);
                col=mix(col,vec3(1.0,.92,.38),mote);
                alpha=max(alpha,mote*.9);
                outColor=vec4(clamp(col,0.0,1.0),
                    alpha*appear*(.89+.11*phase));
            }
        `;
        const sparkVert=`#version 300 es
            ${sharedFns}
            uniform vec2 uView;
            uniform float uClock,uProgress,uDark,uPhase,uTail,uScale;
            out float vEnergy,vKind;
            float rnd(float x){return hash(vec2(x,x*.713));}
            void main(){
                float id=float(gl_VertexID);
                float t=clamp(uProgress,0.0,1.0);
                float age=fract(rnd(id*1.07+7.3)+uClock*
                                 mix(.16,.46,uDark)*(1.0+rnd(id+11.0)*.9));
                float y=rnd(id*17.7+3.0)*(uView.y+155.0)-68.0-
                    age*mix(71.0,195.0,uDark);
                float dir=mix(-1.0,1.0,uDark);
                float flight=(8.0+age*(170.0+rnd(id*4.2)*280.0));
                float x=stormEdge(y,t,uClock,uView.x,uDark)+
                    dir*flight+sin(id*6.7+uClock*5.0)*age*22.0;
                float tailMix=uPhase;
                float xTail=rnd(id*41.2+13.0)*uView.x+
                    dir*(1.0-uTail)*89.0;
                float yTail=rnd(id*19.1+17.0)*uView.y-
                    (1.0-uTail)*105.0;
                x=mix(x,xTail,tailMix);
                y=mix(y,yTail,tailMix);
                float envelope=smoothstep(.01,.13,t)*
                    (1.0-smoothstep(.89,1.0,t));
                vEnergy=mix(envelope*(1.0-age)*(.64+.62*rnd(id+1.0)),
                            uTail*(.22+.64*(1.0-age)),tailMix);
                vKind=rnd(id*5.9+31.0);
                float size=mix(1.2,6.2,rnd(id+8.0))*
                    mix(.65,1.27,uDark);
                gl_PointSize=max(1.0,size*uScale);
                gl_Position=vec4(x/uView.x*2.0-1.0,
                                 1.0-y/uView.y*2.0,0.0,1.0);
            }`;
        const sparkFrag=`#version 300 es
            precision highp float;
            uniform float uDark,uRenderMode;
            in float vEnergy,vKind;
            out vec4 outColor;
            void main(){
                vec2 p=gl_PointCoord*2.0-1.0;
                p.x*=1.12;
                float radius=dot(p,p);
                if(radius>1.0)discard;
                // Draw real charcoal flecks with normal alpha blending,
                // then hot embers in their own additive pass. Dark shapes
                // would disappear if mixed into a single additive pass.
                if(uRenderMode<.5){
                    if(uDark<.5 || vKind>.23)discard;
                    float irregular=.78+.17*sin(atan(p.y,p.x)*7.0+
                                             vKind*80.0);
                    if(radius>irregular)discard;
                    outColor=vec4(vec3(.023,.017,.019),
                                  (1.0-radius)*vEnergy*.69);
                    return;
                }
                if(uDark>.5 && vKind<.23)discard;
                float a=pow(1.0-radius,2.8)*vEnergy;
                vec3 hot=mix(vec3(.93,.095,.014),vec3(1.0,.85,.36),
                             smoothstep(.18,.90,vKind));
                vec3 blue=mix(vec3(.17,.38,.57),vec3(.45,.68,.75),
                              smoothstep(.2,.8,vKind));
                outColor=vec4(mix(blue,hot,uDark),
                              a*mix(.20,.85,uDark));
            }`;

        // GPU flame geometry, not Canvas pretending to be a WebGL effect.
        // Each instance is an upward-rising, tapered turbulent flame sheet.
        // Varied sizes/positions create hundreds of individual white-hot
        // lobes, replacing flat horizontal gradient bands.
        const plumeVert=`#version 300 es
            ${sharedFns}
            uniform vec2 uView;
            uniform float uClock,uProgress,uDark;
            out vec2 vLocal;
            out float vSeed,vHeat,vAge;
            void main(){
                int v=gl_VertexID;
                vec2 corners[6]=vec2[6](
                    vec2(-1.0,-1.0),vec2(1.0,-1.0),vec2(-1.0,1.0),
                    vec2(-1.0,1.0),vec2(1.0,-1.0),vec2(1.0,1.0));
                vLocal=corners[v];
                float id=float(gl_InstanceID);
                float seed=hash(vec2(id*1.71+8.1,id*.37+2.4));
                float phase=fract(seed+uClock*(.19+
                    .22*hash(vec2(id*.91+2.1,3.4))));
                float y=hash(vec2(id*3.41+9.2,4.1))*
                    (uView.y+220.0)+80.0-
                    phase*(145.0+150.0*seed);
                float span=clamp(uView.x*.225,175.0,475.0);
                float trail=19.0+pow(hash(vec2(id*2.17,5.3)),.75)*
                    span*.88;
                float centerX=stormEdge(y,uProgress,uClock,
                    uView.x,uDark)+trail+
                    sin(uClock*2.9+seed*6.283+phase*5.0)*
                    (7.0+12.0*phase);
                float width=(14.0+50.0*hash(vec2(id*1.93,7.2)))*
                    (.75+.30*sin(phase*3.14159));
                float height=(57.0+131.0*hash(vec2(id*.89,11.1)))*
                    (.76+.25*seed);
                vec2 pos=vec2(centerX+vLocal.x*width,
                    y-vLocal.y*height*.5);
                gl_Position=vec4(pos.x/uView.x*2.0-1.0,
                    1.0-pos.y/uView.y*2.0,0.0,1.0);
                vSeed=seed;
                vAge=phase;
                vHeat=smoothstep(.02,.17,phase)*
                    (1.0-smoothstep(.77,1.0,phase))*
                    sin(3.14159265*uProgress);
            }`;
        const plumeFrag=`#version 300 es
            precision highp float;
            uniform float uClock;
            in vec2 vLocal;
            in float vSeed,vHeat,vAge;
            out vec4 outColor;
            float hash2(vec2 p){
                return fract(sin(dot(p,vec2(127.1,311.7)))*
                    43758.5453123);
            }
            float ns(vec2 p){
                vec2 i=floor(p),f=fract(p);
                f=f*f*(3.0-2.0*f);
                return mix(mix(hash2(i),hash2(i+vec2(1,0)),f.x),
                    mix(hash2(i+vec2(0,1)),hash2(i+1.0),f.x),f.y);
            }
            float turb(vec2 p){
                float f=0.0,a=.56;
                for(int i=0;i<4;i++){
                    f+=a*ns(p);
                    p=mat2(1.72,-1.06,1.06,1.72)*p+8.12;
                    a*=.50;
                }
                return f;
            }
            void main(){
                float rise=(vLocal.y+1.0)*.5;
                vec2 u=vec2(vLocal.x*2.15+vSeed*9.0,
                    rise*4.6-uClock*1.9+vSeed*14.0);
                float warp=turb(u);
                float detail=turb(u*2.3+warp*1.8);
                float swirl=.17*sin(rise*7.2+
                    uClock*3.0+vSeed*12.0)+
                    (warp-.48)*.31;
                float pinch=.13+.79*pow(1.0-rise,.69);
                float cut=abs(vLocal.x+swirl+(detail-.5)*.18);
                float shredded=pinch+(warp-.48)*.22+
                    (detail-.5)*.15;
                float plume=1.0-smoothstep(shredded-.20,
                    shredded+.06,cut);
                plume*=smoothstep(.015,.14,rise)*
                    (1.0-smoothstep(.81,1.02,rise));
                float core=1.0-smoothstep(pinch*.19,
                    pinch*.70,cut);
                core*=smoothstep(.05,.16,rise)*
                    (1.0-smoothstep(.56,.89,rise));
                float flux=smoothstep(.22,.72,warp*.68+
                    detail*.43+.14*sin(rise*8.0+vSeed*11.0));
                float gold=plume*(.56+.44*flux);
                float white=core*(.31+.69*flux);
                vec3 col=mix(vec3(.94,.074,.008),
                    vec3(1.0,.46,.015),clamp(gold,0.0,1.0));
                col=mix(col,vec3(1.0,.91,.36),
                    clamp(gold*.43+white*.55,0.0,1.0));
                col=mix(col,vec3(1.0,.998,.86),
                    clamp(white*.80,0.0,1.0));
                float a=plume*vHeat*(.15+.15*flux)+
                    white*vHeat*.10;
                outColor=vec4(col,clamp(a,0.0,.56));
            }`;

        function compile(type,source){
            const shader=gl.createShader(type);
            gl.shaderSource(shader,source);
            gl.compileShader(shader);
            if(!gl.getShaderParameter(shader,gl.COMPILE_STATUS)){
                const log=gl.getShaderInfoLog(shader);
                gl.deleteShader(shader);
                throw new Error('WebGL shader compilation: '+log);
            }
            return shader;
        }
        function program(v,f){
            const vert=compile(gl.VERTEX_SHADER,v);
            const frag=compile(gl.FRAGMENT_SHADER,f);
            const result=gl.createProgram();
            gl.attachShader(result,vert);gl.attachShader(result,frag);
            gl.linkProgram(result);
            gl.deleteShader(vert);gl.deleteShader(frag);
            if(!gl.getProgramParameter(result,gl.LINK_STATUS)){
                const log=gl.getProgramInfoLog(result);
                gl.deleteProgram(result);
                throw new Error('WebGL program link: '+log);
            }
            const names=['uView','uClock','uProgress','uDark',
                'uPhase','uTail','uScale','uRenderMode'];
            return {program:result,locations:Object.fromEntries(
                names.map(name=>[name,gl.getUniformLocation(result,name)]))};
        }
        function setUniforms(p,clock,progress,phase,tail,scale){
            gl.useProgram(p.program);
            const u=p.locations;
            if(u.uView)gl.uniform2f(u.uView,view[0],view[1]);
            if(u.uClock)gl.uniform1f(u.uClock,clock);
            if(u.uProgress)gl.uniform1f(u.uProgress,progress);
            if(u.uDark)gl.uniform1f(u.uDark,dark?1:0);
            if(u.uPhase)gl.uniform1f(u.uPhase,phase);
            if(u.uTail)gl.uniform1f(u.uTail,tail);
            if(u.uScale)gl.uniform1f(u.uScale,scale);
        }
        function resize(){
            view[0]=innerWidth;view[1]=innerHeight;
            // A denser shader but a smaller framebuffer; smoke is naturally
            // soft, so sub-native resolution is barely visible and avoids
            // excessive GPU load on phones or high-DPI displays.
            // Resolve 10px fracture corners faithfully (V29's .61 was
            // visibly smoothing the very shape that should feel torn).
            const desired=mobile?.62:.82;
            const maxPixels=mobile?330000:1050000;
            const bound=Math.sqrt(maxPixels/Math.max(1,view[0]*view[1]));
            const scale=Math.min(desired,bound,window.devicePixelRatio||1);
            const w=Math.max(1,Math.round(view[0]*scale));
            const h=Math.max(1,Math.round(view[1]*scale));
            if(surface.width!==w||surface.height!==h){
                surface.width=w;surface.height=h;
                gl.viewport(0,0,w,h);
            }
            return w/Math.max(1,view[0]);
        }
        function render(progress,phase,tail,clock){
            if(contextLost||disposed)return false;
            try{
                const scale=resize();
                gl.disable(gl.BLEND);
                gl.clearColor(0,0,0,0);
                gl.clear(gl.COLOR_BUFFER_BIT);
                setUniforms(curtain,clock,progress,phase,tail,scale);
                gl.drawArrays(gl.TRIANGLES,0,3);
                if(dark){
                    gl.enable(gl.BLEND);
                    // Charcoal dust is physically in FRONT of burning
                    // paper but BELOW the incandescent plume layer.
                    setUniforms(sparks,clock,progress,phase,tail,scale);
                    if(sparks.locations.uRenderMode)
                        gl.uniform1f(sparks.locations.uRenderMode,0);
                    gl.blendFuncSeparate(gl.SRC_ALPHA,
                        gl.ONE_MINUS_SRC_ALPHA,gl.ONE,
                        gl.ONE_MINUS_SRC_ALPHA);
                    gl.drawArrays(gl.POINTS,0,mobile?750:1700);

                    gl.blendFuncSeparate(gl.SRC_ALPHA,gl.ONE,
                        gl.ONE,gl.ONE_MINUS_SRC_ALPHA);
                    setUniforms(plumes,clock,progress,phase,tail,scale);
                    const flameCount=Math.round((view[1]/360)*
                        (mobile?42:51)*Math.min(1.45,view[0]/640));
                    gl.drawArraysInstanced(gl.TRIANGLES,0,6,
                        Math.max(20,Math.min(flameCount,mobile?115:210)));

                    // Actual WebGL2 cinders above the flames, in addition
                    // to V25's longer 2D particle streaks.
                    setUniforms(sparks,clock,progress,phase,tail,scale);
                    if(sparks.locations.uRenderMode)
                        gl.uniform1f(sparks.locations.uRenderMode,1);
                    gl.drawArrays(gl.POINTS,0,mobile?1500:3300);
                    gl.disable(gl.BLEND);
                }
                // The atmosphere callback paints background soot on a
                // lower canvas and white-hot embers on the upper one.
                return true;
            }catch(error){
                console.warn('[KuranokaPageTransition] GPU frame error:',error);
                contextLost=true;
                return false;
            }
        }
        function onContextLost(event){
            event.preventDefault();
            contextLost=true;
            console.warn('[KuranokaPageTransition] GPU context lost; '+
                'continuing with native navigation.');
        }
        function dispose(){
            if(disposed)return;
            disposed=true;
            cancelAnimationFrame(raf);
            surface.removeEventListener('webglcontextlost',onContextLost);
            window.removeEventListener('pagehide',dispose);
            if(!contextLost){
                try{
                    if(curtain)gl.deleteProgram(curtain.program);
                    if(sparks)gl.deleteProgram(sparks.program);
                    if(plumes)gl.deleteProgram(plumes.program);
                }catch(_){}
            }
            surface.remove();
        }
        try{
            gl=surface.getContext('webgl2',{
                alpha:true,antialias:false,depth:false,stencil:false,
                // We intentionally render at ~30fps. Retain the last
                // frame between GPU submissions to avoid blank flashes.
                premultipliedAlpha:false,preserveDrawingBuffer:true,
                powerPreference:mobile?'low-power':'high-performance'
            });
            if(!gl){surface.remove();return null;}
            curtain=program(backgroundVert,dominantFireFrag);
            if(dark){
                plumes=program(plumeVert,plumeFrag);
                sparks=program(sparkVert,sparkFrag);
            }
            // No abstract, additive GPU spark pass: P3's fire requires
            // textured smoke and incandescent streaks, not neon points.
            gl.disable(gl.DEPTH_TEST);
            gl.disable(gl.SCISSOR_TEST);
            gl.disable(gl.CULL_FACE);
            surface.addEventListener('webglcontextlost',onContextLost);
            window.addEventListener('pagehide',dispose,{once:true});
            window.__kkptRenderer='WebGL2';
        }catch(error){
            console.warn('[KuranokaPageTransition] WebGL unavailable. '+
                'Using Canvas 2D fallback.',error);
            dispose();
            return null;
        }
        return {
            surface,
            dispose,
            attachAtmosphere(draw){attachedAtmosphere=draw;},
            play(duration){
                return new Promise(resolve=>{
                    let started=null,lastDraw=-Infinity,lastClip=-Infinity;
                    function tick(now){
                        if(started===null)started=now;
                        if(disposed||contextLost){resolve();return;}
                        const t=Math.min(1,(now-started)/duration);
                        const clock=now/1000;
                        const edge=makeEdge(t,clock,dark,innerWidth);
                        atmosphereEdge=edge;
                        window.__kkptVisualDark=dark;
                        if(now-lastClip>=(mobile?35:25)||t>=1){
                            clipFrame(edge);
                            lastClip=now;
                        }
                        if(now-lastDraw>=(mobile?43:34)||t>=1){
                            if(!render(t,0,0,clock)){resolve();return;}
                            if(attachedAtmosphere){
                                attachedAtmosphere(clock,Math.min(t,.985),dark,
                                    (now-started)/1000,[]);
                            }
                            lastDraw=now;
                        }
                        if(t<1)raf=requestAnimationFrame(tick);
                        else resolve();
                    }
                    raf=requestAnimationFrame(tick);
                });
            },
            dissipate(duration){
                return new Promise(resolve=>{
                    let started=null,lastDraw=-Infinity;
                    function tick(now){
                        if(started===null)started=now;
                        if(disposed||contextLost){resolve();return;}
                        const t=Math.min(1,(now-started)/duration);
                        if(now-lastDraw>=(mobile?50:40)||t>=1){
                            if(!render(1,1,Math.pow(1-t,1.25),now/1000)){
                                resolve();return;
                            }
                            lastDraw=now;
                        }
                        if(t<1)raf=requestAnimationFrame(tick);
                        else resolve();
                    }
                    raf=requestAnimationFrame(tick);
                });
            }
        };
    }

    // Canvas 2D fallback: deliberately retained for WebGL-disabled
    // browsers, software rendering, or shader compilation failures.
    function canvasFire(canvas,dark,duration,drawAtmosphere,done) {
        const ctx=dark&&canvas
            ? canvas.getContext('2d',{alpha:true,desynchronized:true})
            : null;
        if(dark&&!ctx){done();return;}
        const art=dark?makeSprites():null;
        const w=innerWidth,h=innerHeight;
        if(ctx){
            const scale=Math.min(window.devicePixelRatio||1,w<650?.69:.80);
            canvas.width=Math.max(1,Math.round(w*scale));
            canvas.height=Math.max(1,Math.round(h*scale));
            ctx.setTransform(scale,0,0,scale,0,0);
        }

        const rand=(a,b)=>a+Math.random()*(b-a);
        const mobile=w<650;
        const maxCount=mobile?160:250;
        const p=[];
        const accum={flame:0,ember:0,shard:0,sky:0,mist:0,pollen:0};
        const rates=dark
            ? {flame:mobile?80:105,ember:mobile?72:96,
               shard:mobile?26:42}
            : {sky:mobile?50:80,mist:mobile?13:20,pollen:mobile?27:50};
        const started=performance.now();
        let previous=started;
        let lastPaint=0;
        let lastClip=0;
        function spawn(kind,edge,seconds) {
            if(p.length>=maxCount)return;
            const y=rand(-25,h+25);
            const x=edge(y);
            const type=kind;
            const smoke=type==='smoke';
            const shard=type==='shard';
            const ember=type==='ember'||type==='pollen';
            const blue=type==='sky'||type==='mist'||type==='pollen';
            let radius,life,vx,vy;
            if(shard){
                radius=rand(4,18);life=rand(.6,1.65);
                vx=rand(-130,65);vy=rand(-125,30);
            }else if(smoke){
                radius=rand(32,85);life=rand(1.1,2.5);
                vx=rand(-20,65);vy=rand(-88,-22);
            }else if(type==='mist'){
                radius=rand(45,100);life=rand(.9,1.8);
                vx=rand(-35,45);vy=rand(-75,-15);
            }else if(type==='flame'){
                radius=rand(20,57);life=rand(.3,.82);
                vx=rand(-100,30);vy=rand(-180,-45);
            }else{
                radius=ember?rand(2.5,9):rand(18,47);
                life=ember?rand(.45,1.1):rand(.35,.85);
                vx=rand(-95,75);vy=rand(-150,-25);
            }
            p.push({
                type,life,left:life,
                x:x+rand(smoke?12:shard?-35:-27,smoke?140:shard?36:64),
                y:y+rand(-14,14),vx,vy,radius,
                angle:rand(-Math.PI,Math.PI),spin:rand(-5,5),
                drift:rand(-.65,.65),blue
            });
        }
        function spawnAtRate(dt,edge,seconds,strength){
            for(const type in rates){
                accum[type]+=rates[type]*dt*strength;
                const n=Math.min(11,Math.floor(accum[type]));
                accum[type]-=n;
                for(let i=0;i<n;i++)spawn(type,edge,seconds);
            }
        }
        function advance(dt){
            for(let i=p.length-1;i>=0;i--) {
                const q=p[i];
                q.left-=dt;
                if(q.left<=0){p[i]=p[p.length-1];p.pop();continue;}
                q.x+=q.vx*dt;
                q.y+=q.vy*dt;
                q.vx+=q.drift*dt*35;
                q.vy-=10*dt;
                q.angle+=q.spin*dt;
            }
        }
        function spriteDraw(image,x,y,sx,sy,alpha){
            ctx.globalAlpha=alpha;
            ctx.drawImage(image,x-sx,y-sy,sx*2,sy*2);
        }
        function drawSmoke(fade){
            ctx.globalCompositeOperation='source-over';
            for(const q of p){
                if(q.type!=='smoke'&&q.type!=='mist')continue;
                const age=1-q.left/q.life;
                const radius=q.radius*(1+age*.98);
                const alpha=(q.type==='smoke'?.76:.32)*
                    Math.min(1,age*5)*Math.min(1,q.left/.55)*fade;
                spriteDraw(q.type==='smoke'?art.smoke:art.mist,
                    q.x,q.y,radius*1.7,radius*1.3,alpha);
            }
            ctx.globalAlpha=1;
        }
        function drawShards(fade) {
            if(!dark)return;
            ctx.save();
            ctx.globalCompositeOperation='source-over';
            for(const q of p){
                if(q.type!=='shard')continue;
                const age=1-q.left/q.life;
                const a=Math.min(1,q.left/.38)*(.90-age*.28)*fade;
                ctx.save();
                ctx.translate(q.x,q.y);
                ctx.rotate(q.angle);
                ctx.globalAlpha=a;
                const r=q.radius;
                ctx.beginPath();
                ctx.moveTo(-r*.9,-r*.3);
                ctx.lineTo(r*.7,-r*.75);
                ctx.lineTo(r*.48,r*.42);
                ctx.lineTo(-r*.35,r*.8);
                ctx.closePath();
                ctx.fillStyle=age<.3?'#371d22':'#140d13';
                ctx.fill();
                ctx.strokeStyle=age<.42?'#f57d3c':'#5a2c2b';
                ctx.lineWidth=age<.42?1.6:.75;
                ctx.stroke();
                ctx.restore();
            }
            ctx.restore();
        }
        function drawCore(edge,seconds,t,fade){
            const waviness=Math.sin(Math.PI*t);
            ctx.save();
            ctx.beginPath();
            const count=Math.max(35,Math.ceil(h/19));
            for(let i=0;i<=count;i++){
                const y=h*i/count;
                if(i===0)ctx.moveTo(edge(y),y);
                else ctx.lineTo(edge(y),y);
            }
            ctx.lineCap='round';
            ctx.lineJoin='round';
            if(dark){
                ctx.globalCompositeOperation='lighter';
                ctx.globalAlpha=fade;
                ctx.shadowColor='#ff3903';
                ctx.shadowBlur=25;
                ctx.strokeStyle='rgba(255,55,5,.82)';
                ctx.lineWidth=43;
                ctx.stroke();
                ctx.shadowBlur=16;
                ctx.strokeStyle='#ff9b17';
                ctx.lineWidth=20;
                ctx.stroke();
                ctx.shadowBlur=7;
                ctx.strokeStyle='#ffe45e';
                ctx.lineWidth=9;
                ctx.stroke();
                ctx.shadowBlur=4;
                ctx.strokeStyle='#fffcde';
                ctx.lineWidth=3.8;
                ctx.stroke();
            }else{
                ctx.globalAlpha=fade*.64;
                ctx.shadowColor='#8ccfff';
                ctx.shadowBlur=29;
                ctx.strokeStyle='rgba(139,219,255,.68)';
                ctx.lineWidth=28;
                ctx.stroke();
                ctx.shadowBlur=10;
                ctx.strokeStyle='#e7f8ff';
                ctx.lineWidth=9;
                ctx.stroke();
                ctx.shadowBlur=0;
                ctx.strokeStyle='white';
                ctx.lineWidth=2;
                ctx.stroke();
            }
            ctx.restore();

            // Dense GOLD / WHITE rolling fire, including on both sides
            // of the border. These are the luminous shapes from V2.
            if(dark){
                ctx.save();
                ctx.globalCompositeOperation='lighter';
                for(let y=-70;y<h+80;y+=48){
                    const x=edge(y);
                    const pulse=.65+.35*Math.sin(seconds*8.5+y*.083);
                    spriteDraw(art.flame,x+rand(-8,30),y,77,70,
                        fade*(.26+.16*pulse));
                }
                for(let y=-20;y<h+52;y+=36){
                    const x=edge(y);
                    const flicker=Math.sin(seconds*13+y*.19);
                    const length=52+30*flicker+17*Math.sin(seconds*6-y*.11);
                    const lean=15+18*Math.sin(seconds*9+y*.069);
                    ctx.globalAlpha=.62*fade;
                    ctx.fillStyle='#ff5705';
                    ctx.beginPath();
                    ctx.moveTo(x+18,y+19);
                    ctx.bezierCurveTo(x-18,y+2,x-lean-24,y-length*.57,
                        x-lean,y-length);
                    ctx.bezierCurveTo(x+2,y-length*.57,x+13,y-12,x+18,y+19);
                    ctx.fill();
                    ctx.globalAlpha=.58*fade;
                    ctx.fillStyle='#ffdb58';
                    ctx.beginPath();
                    ctx.moveTo(x+7,y+8);
                    ctx.quadraticCurveTo(x-10,y-length*.33,
                        x-lean*.8,y-length*.72);
                    ctx.quadraticCurveTo(x+3,y-length*.30,x+8,y+8);
                    ctx.fill();
                    ctx.globalAlpha=.38*fade;
                    ctx.fillStyle='#fffced';
                    ctx.beginPath();
                    ctx.moveTo(x+3,y+5);
                    ctx.quadraticCurveTo(x-5,y-length*.2,
                        x-lean*.5,y-length*.48);
                    ctx.quadraticCurveTo(x+4,y-length*.19,x+5,y+5);
                    ctx.fill();
                }
                ctx.restore();
            }else{
                ctx.save();
                ctx.globalCompositeOperation='lighter';
                for(let y=-50;y<h+55;y+=88){
                    spriteDraw(art.sky,edge(y),y,89,109,.27*fade);
                }
                ctx.restore();
            }
        }
        function drawBrightParticles(fade) {
            ctx.save();
            ctx.globalCompositeOperation='lighter';
            for(const q of p){
                if(q.type==='smoke'||q.type==='mist'||q.type==='shard')continue;
                const age=1-q.left/q.life;
                const brightness=Math.min(1,q.left/.25)*(1-age*.25)*fade;
                let artName='flame',sx=q.radius,sy=q.radius;
                if(q.type==='ember'){artName='ember';sx*=1.2;sy*=1.2;}
                else if(q.type==='pollen'){artName='sky';sx*=1.15;sy*=1.15;}
                else if(q.type==='sky'){artName='sky';sx*=1.1;sy*=1.55;}
                else {sx*=.9;sy*=1.65;}
                spriteDraw(art[artName],q.x,q.y,sx,sy,
                    brightness*(q.type==='ember'?.93:.78));
            }
            ctx.restore();
            ctx.globalAlpha=1;
            ctx.globalCompositeOperation='source-over';
        }
        function paint(now) {
            const t=Math.min(1,(now-started)/duration);
            const seconds=now/1000;
            const edge=makeEdge(t,seconds,dark,w);
            // Clip-path polygon reconstruction can cause expensive iframe
            // compositor work. It runs at a bounded rate independent of rAF.
            atmosphereEdge=edge;
            window.__kkptVisualDark=dark;
            if(now-lastClip>=(mobile?33:23)||t>=1){
                clipFrame(edge);
                lastClip=now;
            }
            if(now-lastPaint<(mobile?35:32) && t<1){
                requestAnimationFrame(paint);return;
            }
            const dt=Math.min(.070,(now-previous)/1000);
            previous=now;lastPaint=now;
            const fade=Math.min(1,t/.055,(1-t)/.045);
            // Restore V14's broad smoke banks, long-lived char, pressure
            // waves and delicate blue leaves. V2 only paints the FIRE.
            drawAtmosphere(seconds,Math.min(t,.925),dark,(now-started)/1000,[]);
            if(dark){
                advance(dt);
                if(t<1)spawnAtRate(dt,edge,seconds,Math.max(0,fade));
                ctx.clearRect(0,0,w,h);
                drawShards(fade);
                drawCore(edge,seconds,t,fade);
                drawBrightParticles(fade);
            }
            if(t<1)requestAnimationFrame(paint);
            else done();
        }
        requestAnimationFrame(paint);
    }

    function setDisplayed(nextActive) {
        active=nextActive;
        frame.classList.toggle('kkpt-active',active);
        document.body.classList.toggle('kkpt-other-active',active);
        frame.style.clipPath=active?'inset(0)':hideClip;
        frame.style.visibility=active?'visible':'hidden';
        frame.style.pointerEvents='';
        frame.tabIndex=active?0:-1;
        frame.setAttribute('aria-hidden',active?'false':'true');
        document.title=active?otherTitle:baseTitle;
        showTheme((active?otherPage:basePage)==='Kuronata');
        // Stop the invisible Kuronata ambience in either document.
        root.classList.toggle('kkpt-world-suspended',basePage==='Kuronata'&&active);
        try{
            frame.contentDocument?.documentElement.classList.toggle(
                'kkpt-frame-inactive',!active);
        }catch(_){}
        updateButton();
    }

    async function animateSwap(nextActive) {
        if(animating)return;
        animating=true;
        button.classList.add('kkpt-busy');
        labelSub.textContent='PREPARING THE OTHER SIDE...';
        if(!loading)warmFrame();
        const ok=await Promise.race([loading,sleep(11000).then(()=>false)]);
        if(!ok||!ready){
            navigateRealPage(nextActive?otherUrl.href:baseUrl);return;
        }
        const dark=(nextActive?otherPage:basePage)==='Kuronata';
        // GPU renderer is compiled while the destination is still hidden.
        // Only the actual fallback needs 17 CPU sprite textures.
        const gpu=createWebGLCurtain(dark);
        if(!gpu || dark){
            if(!gpu)window.__kkptRenderer='Canvas2D';
            await prewarmAtmosphere();
        }
        let gpuAtmosphere=null;
        let gpuFirelight=null;
        if(gpu&&dark){
            gpuAtmosphere=document.createElement('canvas');
            gpuAtmosphere.id='kkpt-atmosphere';
            gpuAtmosphere.setAttribute('aria-hidden','true');
            gpuFirelight=document.createElement('canvas');
            gpuFirelight.id='kkpt-firelight';
            gpuFirelight.setAttribute('aria-hidden','true');
            document.body.append(gpuAtmosphere,gpuFirelight);
            gpu.attachAtmosphere(createAtmosphere(
                gpuAtmosphere,false,gpuFirelight));
        }
        frame.style.visibility='visible';
        frame.classList.add('kkpt-animating');
        // Give the now-visible destination its own first composited frame.
        await new Promise(resolve=>requestAnimationFrame(()=>requestAnimationFrame(resolve)));

        labelSub.textContent=dark?'THE SKY IS BURNING':'DAWN IS BREAKING';
        // When returning to the blue page, force the Day palette
        // BEFORE unmasking it. The dark iframe still fully covers it.
        if(!dark)showTheme(false);
        frame.classList.remove('kkpt-active');
        frame.style.pointerEvents='none';
        frame.style.clipPath=active?'inset(0)':hideClip;

        const duration=dark?3950:3150;
        transitionSound(dark,duration);
        const tail=dark?2150:1450;
        if(gpu){
            try{
                await gpu.play(duration);
                setDisplayed(nextActive);
                if(gpuAtmosphere){
                    gpuAtmosphere.style.transition='opacity '+tail+
                        'ms ease-out,transform '+tail+'ms ease-out';
                    void gpuAtmosphere.offsetWidth;
                    gpuAtmosphere.style.opacity='0';
                    gpuAtmosphere.style.transform=
                        'translate3d(0,-22px,0) scale(1.035)';
                    gpuFirelight.style.transition='opacity '+tail+
                        'ms ease-out,transform '+tail+'ms ease-out';
                    gpuFirelight.style.opacity='0';
                    gpuFirelight.style.transform=
                        'translate3d(0,-22px,0) scale(1.035)';
                }
                await gpu.dissipate(tail);
            }finally{
                gpu.dispose();
                gpuAtmosphere?.remove();
                gpuFirelight?.remove();
            }
        }else{
            // Fully working older Canvas renderer if WebGL2 is unavailable.
            const atmosphere=document.createElement('canvas');
            atmosphere.id='kkpt-atmosphere';
            atmosphere.setAttribute('aria-hidden','true');
            document.body.append(atmosphere);
            const drawAtmosphere=createAtmosphere(atmosphere);
            const canvas=dark?document.createElement('canvas'):null;
            if(canvas){
                canvas.id='kkpt-vfx';
                canvas.setAttribute('aria-hidden','true');
                document.body.append(canvas);
            }
            await new Promise(resolve=>canvasFire(
                canvas,dark,duration,drawAtmosphere,resolve));
            setDisplayed(nextActive);
            if(canvas){
                canvas.style.opacity='0';
                setTimeout(()=>canvas.remove(),210);
            }
            atmosphere.style.transition='opacity '+tail+
                'ms ease-out, transform '+tail+'ms ease-out';
            await new Promise(resolve=>requestAnimationFrame(resolve));
            atmosphere.style.opacity='0';
            atmosphere.style.transform='translate3d(0,-22px,0) scale(1.035)';
            await sleep(tail+70);
            atmosphere.remove();
        }
        animating=false;
        button.classList.remove('kkpt-busy','kkpt-quiet');
        // The iframe was only the moving scenery during the reveal.
        // Hand off to the ACTUAL Wiki page: native sidebars, scrollbar,
        // history, refresh, accessibility and links all work normally.
        navigateRealPage(otherUrl.href);
    }

    function requestSwap(nextActive) {
        if (animating || nextActive === active) return;
        if (matchMedia('(prefers-reduced-motion: reduce)').matches) {
                navigateRealPage(otherUrl.href);
            return;
        }
        animateSwap(nextActive).catch(err => {
            console.error('[KuranokaPageTransition] V30:',err);
            document.getElementById('kkpt-vfx')?.remove();
            document.getElementById('kkpt-atmosphere')?.remove();
            document.getElementById('kkpt-firelight')?.remove();
            document.getElementById('kkpt-webgl')?.remove();
            if (frame) frame.style.filter = '';
            navigateRealPage(nextActive ? otherUrl.href : baseUrl);
        });
    }

    function createButton() {
        if (!document.body || document.getElementById('kkpt-toggle')) return;
        button=document.createElement('a');
        button.id='kkpt-toggle';
        labelIcon=document.createElement('span');
        labelIcon.className='kkpt-icon';
        labelIcon.setAttribute('aria-hidden','true');
        const text=document.createElement('span');
        text.className='kkpt-text';
        labelTitle=document.createElement('span');
        labelSub=document.createElement('span');
        labelSub.className='kkpt-sub';
        text.append(labelTitle,labelSub);
        button.append(labelIcon,text);
        document.body.append(button);
        button.hidden=!SHOW_FLOATING_BUTTON;
        updateButton();
        watchPortalLinks(document, otherPage);
        mountFateGear(document,otherPage);
        warmFrame();
        // WebGL2 has no CPU smoke atlas: defer the 2D fallback until needed.
        preloadRebirthPad();

        button.addEventListener('click', event => {
            if (!isPlainClick(event)) return;
            event.preventDefault();
            primeSound();
            requestSwap(!active);
        });
    }

    // A plain [[Kuronata|your mysterious text]] now triggers everything.
    // The inverse [[Kuranoka|...]] uses the same transition, then real navigation.
    document.addEventListener('click', event => {
        if (active) return;
        portalClick(event, document, otherPage, true);
    }, true);
    mw.hook('wikipage.content').add(() => {
        if (document.readyState !== 'loading') watchPortalLinks(document, otherPage);
    });

    // Browser history is now real document history. A bfcache return
    // must restore THIS document, not leave its animated preview visible.
    window.addEventListener('pageshow', event => {
        if (!event.persisted) return;
        animating=false;
        document.getElementById('kkpt-vfx')?.remove();
        document.getElementById('kkpt-atmosphere')?.remove();
        document.getElementById('kkpt-firelight')?.remove();
        document.getElementById('kkpt-webgl')?.remove();
        if(frame){
            frame.style.filter='';
            setDisplayed(false);
            frame.classList.remove('kkpt-animating');
        }
        button?.classList.remove('kkpt-busy','kkpt-quiet');
    });

    if (document.readyState === 'loading') {
        document.addEventListener('DOMContentLoaded',createButton,{once:true});
    } else {
        createButton();
    }
}());