JS1k: The JavaScript code golfing competition

(function(b,d,e,f,g){var h=[],j=Array(b*(d+4)).fill(0),k=c.createImageData(b,d+4),l=Math,i=document.createElement("canvas"),m=i.getContext("2d");i.width=e+1;let n=m.createLinearGradient(0,0,e+1,0);n.c=n.addColorStop,n.c(0,"#000"),n.c(.45,"#000"),n.c(.5,"#080"),n.c(.6,"#ff0"),n.c(.9,"#fff"),n.c(1,"#fff"),m.fillStyle=n,m.fillRect(0,0,e+1,10);let o=m.getImageData(0,0,e+1,1);for(let j=0;j<=e;j++)h.push([o.data[4*j],o.data[4*j+1],o.data[4*j+2],255]);a.addEventListener("mousemove",function(b){var d=a.getBoundingClientRect(),f=b.clientX-d.left,h=b.clientY-d.top;if(h<d.bottom-g&&h>g)for(let b=0;b<g;b++)for(let i=0;i<g;i++)j[f-7+i+d.right*(h+1+b-7)]=e},!1),function g(){for(let d=b+1;d<j.length-b+1;d++)j[d-b]=j[d-b]+j[d-1]+j[d+1]+j[d+b]>>>2;for(let g=0;g<b;g++)if(0==g%5){let h=e-l.round(l.random()*(e-f));for(let e=0;4>e;e++)for(let f=0;5>f;f++)j[g+f+b*(d/1+1+e-0)]=h}for(let b=0;b<j.length;b++)for(let d=0;4>d;d++)k.data[4*b+d]=h[j[b]][d];c.putImageData(k,0,0),requestAnimationFrame(g)}()})(a.width,a.height,512,40,20);

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

Original source not submitted