CANVAS animation

color change

HTML

<CANVAS id="canvas" width="400px" height="300px"></CANVAS>

CSS

canvas{border:1px solid black; height: 100%; width: 100%;}

JavaScript

var canvas, 
        context,
        bounce = -1,
        r = 0,
        g=150,
        b=250;

        
    
    canvas = $("#canvas")[0];
    context = canvas.getContext("2d");

context.fillStyle="#000000";

    var width = canvas.width;
    var height = canvas.height;

var a = Math.ceil(Math.random() * 10)
var point = {x:1,y:a,vx:1,vy:1};
        
setInterval(draw, 1000/500);
 
    function draw() {
       context.clearRect(0, 0, 500, 500);
           
     //   r= getR(r,5)
    //    g= getR(r,15)
     //   b= getR(r,30)
        
        
        var xx =  "rgb(" + r + ","+ g +","+ b +")";
 
         context.fillStyle= xx;
 
         a = Math.ceil(Math.random() * 10)
        
        
        Circle(point.x, point.y, 20, 0, Math.PI * 2, false);

        
        point.x += (Math.random() >= .5) ? point.vx - a  : point.vx + 2 * a ;
        point.y +=  (Math.random() >= .5) ? point.vx  + a +1 : point.vx -a ;
        if(point.x > width) {
                point.x = width;
                point.vx *= bounce;
            }
            else if(point.x < 0) {
                point.x = 0;
                point.vx *= bounce;
            };
            if(point.y > height) {
                point.y = height;
                point.vy *= bounce;
            }
            else if(point.y < 0) {
                point.y = 0;
                point.vy *= bounce;
            };
        
    };


 
function getR(color, inc){
   var color = color;
    
    if(Math.random() >= .5){
    
     color =   color - inc;
    
    } else {
    
       color =   color + inc;
    }
    
    if(color + inc >= 255){
       
        color =254;

    }   
        if(color - inc <= 0){
      
        color = 1;
        } 
    
    
    return  color;

}






//+++++++++++++++++++++++++++++++++++++++++
//     CANVVAS UTILITIEZ
//+++++++++++++++++++++++++++++++++++++++++

function randomcolor(){
    var r=Math.floor(Math.random()*255),
        g=Math.floor(Math.random()*255),
       ...