JS1k: The JavaScript code golfing competition

D=b.style,f=window;D.margin=0;D.overflow="hidden";i=f.innerWidth,j=f.innerHeight;c.width=i;c.height=j;k=Math,l=k.random,n=k.sin,p=k.floor,q=20,r=[],s=k.PI;function t(d){d.b=d.x=(l()*i-i*.5)*q;d.c=d.y=(l()*j-j*.2)*q;d.a=q;d.d=l()}for(var v=0,w;v<300;v++){w={};t(w);r.push(w)}setInterval(function(){a.fillStyle="rgba(0,0,0,.6)";a.fillRect(0,0,i,j);for(var d=0;d<300;d++){var b=r[d],o=n(s)*32-16,u=b.x/b.a,e=u+i/2-o,g=o=b.y/b.a,m=l()*360,x=b.a>q-5?(q-b.a)/5:1,h=q-b.a-4;a.fillStyle="hsla("+p(m)+",50%,85%,"+x+")";a.beginPath();if(b.a<q-6){a.save();a.translate(e,g);a.rotate(b.d*(d%2?1:-1)*(d%3/2+.1));g=0;e=h/(d%4+2);for(m=h/(d%3+1);g<6;g++){a.lineTo(-e,m);a.lineTo(0,h);a.lineTo(e,m);a.lineTo(0,0);a.rotate(k.PI/3)}a.fill();if(d%2==0){g=0;for(e=h/(d%5+1);g<6;g++){a.beginPath();a.moveTo(0,h);a.lineTo(-e,h-e);a.lineTo(0,h-e);a.lineTo(e,h-e);a.fill();a.rotate(k.PI/3)}}a.restore()}else{a.arc(e,g,1/b.a*5+1,0,k.PI*2,true);a.fill()}b.b=u;b.c=o;b.a-=.15;b.d+=l()/5;if(b.a<.15||b.b<-i/2||b.b>i/2||b.c>j)t(b);s+=k.PI/2}},25);

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

// remove frame margin and scrollbars when max out size of canvas
var ds = document.body.style;
ds.margin = "0px";
ds.overflow = "hidden";

// get dimensions of window and resize the canvas to fit
var win = window,
    width = win.innerWidth,
    height = win.innerHeight,
    mousex = width/2, mousey = height/2;
c.width=width;
c.height=height;

// setup aliases
var M = Math,
    Rnd = M.random,
    Sin = M.sin,
    Flr = M.floor;

// constants and storage for objects that represent snow flake positions
var depth = 20,
    units = 300, //500
    flakes = [],
    Z = 0.15,
    SA=M.PI;

// function to reset a flake object
function resetFlake(f)
{
   f.px = f.x = (Rnd() * width - (width * 0.5)) * depth;
   f.py = f.y = (Rnd() * height - (height * 0.2)) * depth;
   f.z = depth;
   f.s = Rnd();   // random seed for each snowflake
}

// initial flake setup
for (var i=0, n; i<units; i++)
{
   n = {};
   resetFlake(n);
   flakes.push(n);
}

// star rendering anim function
setInterval(function()
{
   // clear background
   a.fillStyle = "rgba(0,0,0,0.8)";
   a.fillRect(0, 0, width, height);
   
   // update all flakes
   for (var i=0; i<units; i++)
   {
      var n = flakes[i],
          w = Sin(SA) * 32 - 16,
          xx = n.x / n.z,
          nx = xx + width/2 - w,
          yy = n.y / n.z,// + w,
          ny = yy,
          // colour sparkle
          hue = Rnd() * 360,
          // fog alpha fade in
          alpha = n.z > depth - 5 ? (depth - n.z)/5 : 1,
          // start radius of LOD snowflake
          rad = depth - n.z - 4;
      
      // fade in (fog effect) using alpha value
      a.fillStyle = "hsla(" + Flr(hue) + ",50%,90%," + alpha + ")";
      a.beginPath();
      if (n.z < depth - 6)
      {
         // LOD snowflake graphic
         a.save();
         a.translate(nx, ny);
         // randomize the initial snowflake rotation a bit
         a.rotate(n.s * (i%2 ? 1 : -1) * ((i%3)/2 + 0.1));
         
         // render basic star style snowflake
         for (var m=0,g=rad/(i%4+2),h=rad/(i%3+1); m<6; m++)
         {
            a.lineTo(-g, h);
            a.lineTo(0, rad);
            a.lineTo(g, h);
            a.lineTo(0, 0);
            a.rotate(M.PI / 3);
         }
         a.fill();
         
         // render spikes on each spoke
         if (i % 2 == 0)
         {
            for (var s=0,g=rad/(i%5+1); s<6; s++)
            {
               a.beginPath();
               a.moveTo(0, rad);
               a.lineTo(-g, rad-g);
               a.lineTo(0, rad-g);
               a.lineTo(g, rad-g);
               a.fill();
               a.rotate(M.PI / 3);
            }
         }
         
         a.restore();
      }
      else
      {
         // modify x and y position slightly by randomized sinwave
         a.arc(nx, ny, 1/n.z * 5 + 1, 0, M.PI*2, true);
         a.fill();
      }
      
      // update flake position and sinewave offset state
      n.px = xx;
      n.py = yy;
      n.z -= Z;
      n.s += Rnd()/5;
      
      // reset when flake is out of the view field
      if (n.z < Z || n.px < -width/2 || n.px > width/2 || n.py > height)
      {
         // reset flake
         resetFlake(n);
      }
      
      SA += M.PI/2;
   }
}, 25);