/**
 * This uncompressed source is close to my entry submitted to JS1k.
 * The number of particles and colours are different, but the rest is
 * near enough the same. The code is structured in a much neater way.
 */
var animate = function(){
    //Grab our canvas object and context
    var canvas = document.getElementById('c');
    var c = canvas.getContext('2d');
   
    //Set the canvas width to the same as the browser
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;
   
    //Make the body background black and hide the scroll bars
    document.body.style.background = "black";
    document.body.style.overflow = "hidden";
   
    //Grab the width / height of the canvas for later use
    var width = canvas.width,
    height = canvas.height;
   
    //Arrays used to store the position / speed / direction and radius of the particles
    var posY = [],
    posX = [],
    speedX = [],
    speedY = [],
    directionX = [],
    directionY = [],
    radius = [];
   
    return {
        //Our initialise function
        init: function(){
            //Look at the width and generate a number of particles
            for(i = 10; i < width; i += 30) {
               
                //For each ballplace it in a random location
                var generatedX = Math.floor(Math.random()*width);
                var generatedY = Math.floor(Math.random()*height);
               
                //Set the initial particle start positions
                posX[i] = generatedX;
                posY[i] = generatedY;
               
                //Each particle has a random x and y speed
                var generatedSpeedX = 1 + Math.ceil(Math.random()*8);
                var generatedSpeedY = 1 + Math.ceil(Math.random()*8);
               
                //Set the initial speeds
                speedX[i] = generatedSpeedX;
                speedY[i] = generatedSpeedY;
               
                //Set the x and y directions of each particle
                (Math.ceil(Math.random()*2) === 1) ? directionX[i] = 1 : directionX[i] = -1;
                (Math.ceil(Math.random()*2) === 1) ? directionY[i] = 1 : directionY[i] = -1;
               
                //Each particle has a different radius
                radius[i] = 10 + Math.ceil(Math.random()*5);
            }
           
            //Fire our draw function every 10ms
            setInterval(this.draw, 20);
        },
        //Fun this function to draw a frame
        draw: function(){
            //Clear the last frame by filling it black (clearRect caused issues in chrome)
            c.fillStyle = "black";
            c.fillRect(0,0,width,height);
               
                //Loop through each particle
                for(i=10;i<width;i+=30){
                   
                    //Change its x direction if it gets to the boundry
                    if(posX[i] > width || posX[i] < 0){
                        directionX[i] *= -1;
                    }
                    //Change its y direction if it gets to the boundry
                    if(posY[i] > height || posY[i] < 0){
                        directionY[i] *= -1;
                    }
                   
                    //Save the canvas settings before we modify anything (clip)
                    c.save();//Before path
                   
                        //For each particle begin a path around its position
                        c.beginPath();
                        c.arc(posX[i],posY[i],radius[i],0,Math.PI * 2,false);
                        //Clip the path ready to be filled later
                        c.clip();
                       
                        //Set the red radial gradient alpha to 1
                        c.globalAlpha = 1;
                       
                        //Create our red radial gradient up the top left corner
                        var radGradRed = c.createRadialGradient(width/4,height/4,100,width/4,height/4,width/4);
                        radGradRed.addColorStop(0, 'red');
                        radGradRed.addColorStop(1, 'black');
                        c.fillStyle = radGradRed;
                       
                        //Create a rectangle filled using the red radial
                        c.fillRect(0,0,width,height);
                       
                        //Set the global alpha to 0.6 for the next box (so the red shines through)
                        c.globalAlpha = 0.6;
                       
                        //Create our green radial gradient up the top right corner
                        var radGradGreen = c.createRadialGradient(3*width/4,height/4,100,3*width/4,height/4,width/4);
                        radGradGreen.addColorStop(0, 'green');
                        radGradGreen.addColorStop(1, 'black');
                        c.fillStyle = radGradGreen;
                       
                        //Create a rectangle filled using the green radial
                        c.fillRect(0,0, width, height);
           
                        //Set the global alpha to 0.4 for the next box (red / green shines through)
                        c.globalAlpha = 0.4;
                       
                        //Create our blue radial gradient at the bottom middle
                        var radGradBlue = c.createRadialGradient(width/2,3*height/4,100,width/2,3*height/4,width/4);
                        radGradBlue.addColorStop(0, 'blue');
                        radGradBlue.addColorStop(1, 'black');
                        c.fillStyle = radGradBlue;
                       
                        //Create a rectangle filled using the green radial
                        c.fillRect(0,0,width,height);
                   
                    //Restore the canvas to how it was before the clipping path
                    c.restore();
                   
                    //Set the new x and y position of the selected particle
                    posX[i] += directionX[i]*speedX[i];
                    posY[i] += directionY[i]*speedY[i];
                }
           
            //Set the new global alpha to 0.9 for the static particles
            c.globalAlpha = 0.9;
           
            //Create a red particle top left
            c.fillStyle = "red";
            c.beginPath();
            c.arc(width/4,height/4, 20, 0, Math.PI * 2, false);
            c.fill();
           
            //Create a green particle top right
            c.fillStyle = "green";
            c.beginPath();
            c.arc(3*width/4, height/4, 20, 0, Math.PI * 2, false);
            c.fill();
           
            //Create a blue particle middle bottom
            c.fillStyle = "blue";
            c.beginPath();
            c.arc(width/2, 3*height/4, 20, 0, Math.PI * 2, false);
            c.fill();
        }
    };
}();

//Call the init function and get the particles moving
animate.init();