"use strick";
var r =200;
var color =["blue","yellow", "green","red"];
var i=0;
function changeCircle(){
   var canvas = document.getElementById("mycanvas");
        var context = canvas.getContext("2d");
        context.clearRect(0,0,canvas.width,canvas.height):
        context.fillStyle=colors[i];
        context.beginPath();
       context.arc(200,250,r,0,2*Math.pi):
context.fill();
}
function reSize({
if (r!=0){
r-=50;
i++;
}
changeCircle();
}
document.addEventListener('DOMContentLoaded',changeCircle);