JS1k: The JavaScript code golfing competition

E=253;$=Math.random;T=(c=document.body.children[L=i=0]).getContext('2d');for(c.width=c.height=S=400;i<S;i++)T.fillStyle='hsl('+i*.9+',100%,50%)',T.fillRect(i,0,1,S/4);c.style.background='#000';D=(I=T.getImageData(0,0,S,S)).data;B=[{x:S/2,y:S/2,a:E,b:0,c:0,v:5,V:-4}];N=4e4;M=setInterval('i=B.length;while(b=B[--i]){v=b.v;j=s=Math.sqrt(v*v+b.V*b.V)|0;r=Math.atan2(b.V,b.v);b.f&&(b.V+=.1);while(j--)b.x+=v/s,b.y+=b.V/s,x=b.x|0,y=b.y|0,z=(x+y*S)*4+3,(x<0&&v<0)||(x>S&&v>0)?v=b.v*=-1:y<0&&b.V<0?b.V*=-1:y>S?(B.splice(i,1),j=0):y>360&&y<369&&x>L-25&&x<L+25&&b.V>0?(b.V*=-1,b.f&&(b.v=$()*9,b.V=$()*9+1),b.f=0):D[z]==255?b.f||(D[z]=0,B.push({x:x,y:b.y,a:D[z-3],b:D[z-2],c:D[z-1],v:Math.cos(r+Math.PI*2/(30*$())-15)*3,V:1,f:1}),b.V*=-1,N--):x>0&&x<S&&y>=0&&y<S&&(D[z-3]=b.a,D[z-2]=b.b,D[z-1]=b.c,D[z]=E)}T.putImageData(I,0,0);for(i=3;i<64e4;i+=4)D[i]<=E&&(D[i]*=.9);T.fillRect(L-25,360,50,9);N||clearInterval(M)',32);onmousemove=function(e){L=e.pageX-8};onclick=function(e){B.push({x:e.pageX-8,y:360,v:$()*9,V:$()*9+1,a:E,b:E,c:E})}

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

(function(E,$,T,c,L,i,S,D,I,B,N,M){
E=253;
$=Math.random;
T=(c=document.body.children[L=i=0]).getContext('2d');
for(c.width=c.height=S=400;i<S;i++)T.fillStyle='hsl('+i*.9+',100%,50%)',T.fillRect(i,0,1,S/4);
c.style.background='#000';
D=(I=T.getImageData(0,0,S,S)).data;
B=[{x:S/2,y:S/2,a:E,b:0,c:0,v:5,V:-4}];
N=4e4;
M=setInterval(function(i,b,j,s,r,x,y,z){
  i=B.length;
  while(b=B[--i]){
    v=b.v;
    j=s=Math.sqrt(v*v+b.V*b.V)|0;
    r=Math.atan2(b.V,b.v);
    b.f&&(b.V+=.1);
    while(j--)
      b.x+=v/s,
      b.y+=b.V/s,
      x=b.x|0,
      y=b.y|0,
      z=(x+y*S)*4+3,
      (x<0&&v<0)||(x>S&&v>0) ? v=b.v*=-1:
      y<0&&b.V<0 ? b.V*=-1:y>S ? (B.splice(i,1),j=0):
      y>360&&y<369&&x>L-25&&x<L+25&&b.V>0? (b.V*=-1,b.f&&(b.v=$()*9,b.V=$()*9+1),b.f=0):
      D[z]==255 ? b.f||(D[z]=0,B.push({x:x,y:b.y,a:D[z-3],b:D[z-2],c:D[z-1],v:Math.cos(r+Math.PI*2/(30*$())-15)*3,V:1,f:1}),b.V*=-1,N--):
      x>0&&x<S&&y>=0&&y<S&&(D[z-3]=b.a,D[z-2]=b.b,D[z-1]=b.c,D[z]=E)
  }
  T.putImageData(I,0,0);
  for(i=3;i<64e4;i+=4){
    D[i]<=E&&(D[i]*=.9);
  }
  T.fillRect(L-25,360,50,9);
  N||clearInterval(M)
},9);
onmousemove=function(e){
  L=e.pageX-8
};
onclick=function(e){
  B.push({x:e.pageX-8,y:360,v:$()*9,V:$()*9+1,a:E,b:E,c:E})
}
})();