JS1k: The JavaScript code golfing competition

ig=document.getElementById("c");ig.width=320;ig.height=240;var p1=0,p2=0,p3=0,p4=0,t1,t2,t3,t4,aSin=[],ti=1,cv=ig.getContext('2d'),cd=cv.createImageData(ig.width,ig.height),rad,i,j,x,idx,as=2.6,fd=0.4,as1=4.4,fd1=2.2,ps=-4.4,ps2=3.3;function init(){var i=512;while(i--){rad=(i*0.703125)*0.0174532;aSin[i]=Math.sin(rad)*1024}}function main(){init();draw()}function rand(va){return Math.random(va)}document.onclick=function(){as=rand(300)*5;fd=rand(300)*10;as1=rand(200)*50;fd2=rand(300)*50;ps=(rand(200)*20)-10;ps2=(rand(200)*40)-20};function draw(){cdData=cd.data;t4=p4;t3=p3;i=320;while(i--){t1=p1+5;t2=p2+3;t3&=511;t4&=511;j=240;while(j--){t1&=511;t2&=511;x=aSin[t1]+aSin[t2]+aSin[t3]+aSin[t4];idx=(i+j*ig.width)*4;cdData[idx+0]=x/as;cdData[idx+1]=x/fd;cdData[idx+2]=x/ps;cdData[idx+3]=255;t1+=5;t2+=3}t4+=as1;t3+=fd1}cd.data=cdData;cv.putImageData(cd,0,0);p1+=ps;p3+=ps2;setTimeout(draw,ti)}main();

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ig = document.getElementById("c");
ig.width = 320;
ig.height = 240;

var p1 = 0,
    p2 = 0,
    p3 = 0,
    p4 = 0,
    t1, t2, t3, t4,
    aSin = [], 
    ti = 1,
    cv = ig.getContext('2d'),
    cd = cv.createImageData(ig.width, ig.height),
    rad,
    i, j, x,
    idx,
    as = 2.6, fd = 0.4, as1 = 4.4, fd1 = 2.2, ps = -4.4, ps2 = 3.3;


function init() {
  var i = 512;
  while (i--) {
    rad = (i * 0.703125) * 0.0174532;
    aSin[i] = Math.sin(rad) * 1024;
  }
}

function main() {
  init();
  draw();  
}

function rand(va) {
  return Math.random(va);
}

document.onclick = function(){
  as = rand(300)*5;
  fd = rand(300)*10;
  as1 = rand(200)*50;
  fd2 = rand(300)*50;
  ps = (rand(200)*20)-10;
  ps2 = (rand(200)*40)-20;
};

function draw() {
	
  cdData = cd.data;	
	
  t4 = p4;
  t3 = p3;

  i = 320; while(i--) {
    t1 = p1 + 5;
    t2 = p2 + 3;

    t3 &= 511;
    t4 &= 511;

    j = 240; while(j--) {
      t1 &= 511;
      t2 &= 511;

      x = aSin[t1] + aSin[t2] + aSin[t3] + aSin[t4];

      idx = (i + j * ig.width) * 4;
      
      cdData[idx + 0] = x/as;
      cdData[idx + 1] = x/fd;
      cdData[idx + 2] = x/ps;
      cdData[idx + 3] = 255;
      
      t1 += 5;
      t2 += 3;
    }

    t4 += as1;
    t3 += fd1;
    
  }
	
  cd.data = cdData;	

  cv.putImageData(cd, 0, 0);

  p1 += ps;
  p3 += ps2;
    
  setTimeout ( draw, ti);
}

main();