JS1k: The JavaScript code golfing competition

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var balls ;

var creating ;  // are we in creation mode?
var level ; 

var i, j ;  // loop variables
var dx,dy ; // difference in x,y position
var dist, theta ; 
var ball2 ;
var ballCount ;
var ballsRemaining ;
var gamePhase = 3; // 0: in game; 1: going to next level; 2: game over

var body = document.body;
var canvas = body['children']['c'];
var ctx = canvas.getContext( '2d' );
var width = canvas.width = innerWidth;
var height = canvas.height = innerHeight-6 ; 
var totalArea = width*height ;
var area ;
var math = Math ;
var rnd = math.random ;
var score ;

body.style.margin = 0 ;

onmouseup = function(){creating=0;}; 
onmousedown = function(event){
                if(!gamePhase)
                    if(ballsRemaining--){
                        // 'creating' is set to 1 in the following statement
                        ballCount = balls.unshift({'x':event.pageX,'y':event.pageY,'r':creating=1,'t':1,'u':0,'v':0});
                    }else{
                        gamePhase=2;
                    }
              };
 
setInterval(

function ()
{
    if (!gamePhase && area > totalArea){
        creating=0; gamePhase = 1; score += 100*(level+ballsRemaining) ;
    }
    
    if (gamePhase){
        if (gamePhase<3){
            alert ((gamePhase-1?'GAME OVER':'LEVEL DONE')+'\nSCORE: '+score) ;
        }
        if (gamePhase&2){
            level = score = 0 ;
        }
        area = creating = gamePhase = 0 ;
        ballsRemaining = ++level + 5 ;
        balls = [] ;
        for (i=0; i < 2*level; i++){
            ballCount = balls.unshift({'x':9+(width-18)*rnd(),'y':9+(height-18)*rnd(),'r':9,'t':0,
                                        'u':2*math.cos(theta=rnd()*math.PI*2),'v':2*math.sin(theta)}) ;
        }
    }
    
    with (ctx){
        fillStyle = "#006" ;
        fillRect(0,0,width, height);
        fillStyle = "blue" ;
        fillRect(0,height-area/width, width, height) ;
        
        area = totalArea/2 ;
        for (i=0; i<ballCount; i++){
          with(balls[i]){
            if (i<creating){    // creating && i==0
                r += 2 ;
                if (x < r || x > width-r || y < r || y > height-r){
                    creating=0 ;
                }
            }
            area += math.PI*r*r ;
            x += u ;
            y += v ;
            if (x < r || x > width-r){
                u = -u ;
            }
            if (y < r || y > height-r){
                v = -v ;
            }
            for (j=0; j<ballCount; j++){
                ball2 = balls[j] ; 
                if (i!=j){
                    dx = x - ball2['x'];
                    dy = y - ball2['y'] ;
                    theta = dx*dx+dy*dy ; // dot product
                    dist = r + ball2['r']; 
                    if (theta < dist*dist){
                        // balls have touched, compute a bounce
                        theta = theta ? 2*(u*dx + v*dy)/theta:0 ;
                        u -= theta*dx ;
                        v -= theta*dy ;
                        if (creating && i==0){
                            creating = 0 ;
                            if(!ball2['t']){
                                balls.shift() ;
                                ballCount-- ; 
                            }
                        }
                        j = ballCount ;  // break
                    }
                }
            }
            beginPath();
            arc(x,y,r,0,math.PI*2,1);
            fillStyle = t ? '#0A0' : 'red';
            fill();
          }
        }
        font = '32px arial' ;
        fillText ('L:'+level+' B:'+ballsRemaining, 50,50) ;
    }
}
, 33);