JS1k: The JavaScript code golfing competition

C=document.getElementById('c');
c=C.getContext('2d');
w=C.width=640;v=C.height=480;W=w*4;X=w*v*4;
c.fillStyle="black";
c.fillRect(0,0,w,v);
function l(){
 d=c.getImageData(0,0,w,v);
 p=d.data;
 for(x=0;x<X;x+=4)p[x]=Math.random()>0.8?255:0;
 c.putImageData(d,0,0)
}
function m(e){
 if(!e)e=window.event;
 if(e.which==32)R=!R;
 if(e.which==65)l();
 if(e.type=="click"){
  d=c.getImageData(0,0,w,v);
  i=(e.clientY-C.offsetTop+pageYOffset)*w+(e.clientX-C.offsetLeft+pageXOffset);
  d.data[4*i]=e.which==1?255:0;
  c.putImageData(d,0,0)
}}
function f(){
 if(R){
  d=c.getImageData(0,0,w,v);
  p=d.data;
  for(x=0;x<X;x+=4){
   s=p[(x-4+X)%X]+p[(x+4)%X]+p[(x+W)%X]+p[(x+W-4)%X]+p[(x+W+4)%X]+p[(x-W+X)%X]+p[(x-W-4+X)%X]+p[(x-W+4+X)%X];
   p[x+1]=s==510?p[x]:s==765?255:0;
  }
  for(x=0;x<X;x+=4)p[x]=p[x+2]=p[x+1];
  c.putImageData(d,0,0)
 }
 setTimeout(f,500);
}
C.onclick=m;
window.onkeydown=m;
l();
R=1;
f();

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

// get the canvas 2d object
C=document.getElementById('c');
c=C.getContext('2d');
// initialize size and size depending values
w=C.width=640;v=C.height=480;W=w*4;X=w*v*4;
// clear the canvas with black
c.fillStyle="black";
c.fillRect(0,0,w,v);

// define a function to add random cells
function l(){
 d=c.getImageData(0,0,w,v);
 p=d.data;
 for(x=0;x<X;x+=4) {
  p[x]=Math.random()>0.8?255:0; // red value 255 marks a cell
 }
 c.putImageData(d,0,0)
}

// the event handler function
function m(e){
 if(!e)e=window.event;
 // toggle on space
 if(e.which==32)R=!R;
 // add cells on 'a'
 if(e.which==65)l();
 // add a cell with left mouse button clicks
 if(e.type=="click"){
  d=c.getImageData(0,0,w,v);
  i=(e.clientY-C.offsetTop+pageYOffset)*w+(e.clientX-C.offsetLeft+pageXOffset);
  d.data[4*i]=e.which==1?255:0;
  c.putImageData(d,0,0)
}}
// this is the main loop, hooked with setTimeout
function f(){
 if(R){ // if not running skip
  d=c.getImageData(0,0,w,v);
  p=d.data;
  // pass 1: calculate next cycle
  for(x=0;x<X;x+=4){
   // use the red values to evaluate the neighbour count
   s=p[(x-4+X)%X]+p[(x+4)%X]+p[(x+W)%X]+p[(x+W-4)%X]+p[(x+W+4)%X]+p[(x-W+X)%X]+p[(x-W-4+X)%X]+p[(x-W+4+X)%X];
   // set the green value with the result:
   // 2 neighbours -> keep the cell
   // 3 neighbours -> create a cell
   // otherwise -> remove the cell
   p[x+1]=s==510?p[x]:s==765?255:0;
  }
  // pass 2: set RGB values
  for(x=0;x<X;x+=4)p[x]=p[x+2]=p[x+1];
  c.putImageData(d,0,0)
 }
 // meet again in 500ms
 setTimeout(f,500);
}
// register the event handler
C.onclick=m;
window.onkeydown=m;
// initial load
l();
// running
R=1;
// start it
f();