Convertir objeto en bola javascript

Hola, estoy haciendo un proyecto en javascript y querría cambiar la figura del cuadrado por una bola. el codigo con (cuadrado).

Código:

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<style>
canvas {
    border:1px solid #d3d3d3;
    background-color: red;
}
</style>
</head>
<body onload="startGame()">
<script>
var myGamePiece;
function startGame() {
    myGamePiece = new component(30, 30, "yellow", 0, 0);
    myGameArea.start();
}
var myGameArea = {
    canvas : document.createElement("canvas"),
    start : function() {
        this.canvas.width = 480;
        this.canvas.height = 270;
        this.context = this.canvas.getContext("2d");
        document.body.insertBefore(this.canvas, document.body.childNodes[0]);
        this.interval = setInterval(updateGameArea, 20);        
    },
    stop : function() {
        clearInterval(this.interval);
    },    
    clear : function() {
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    }
}
function component(width, height, color, x, y, type) {
    this.type = type;
    this.width = width;
    this.height = height;
    this.x = x;
    this.y = y;    
	
    this.speedX = 1;
    this.speedY = 1;    
    this.gravity = 0;
    this.gravitySpeed = 0;
    this.bounce = 0.5;
    this.update = function() {
        ctx = myGameArea.context;
        ctx.fillStyle = color;
        ctx.fillRect(this.x, this.y, this.width, this.height);
    }
    this.newPos = function() {
        this.gravitySpeed += this.gravity;
        this.x += this.speedX;
        this.y += this.speedY + this.gravitySpeed;
        this.hitBottom();
		if(this.x > 450){
		this.speedX = -this.speedX;
		}
		if(this.x < 0){
		this.speedX = -this.speedX;
		}
		if(this.y < 0){
		this.x = x;
		this.y = y;    
		this.speedX = 2;
		this.speedY = 2; 
		this.speedX = 2;
		this.speedY = 2;    
		this.gravity = 0;
		this.gravitySpeed = 0.5;
		this.bounce = 5;		
		}
		if((this.x > 0)&&(this.x<250)&&(this.y>100) && this.speedY > 0){
		this.speedY = -this.speedY;
		
		}
		
    }
	
	
    this.hitBottom = function() {
        var rockbottom = myGameArea.canvas.height - this.height;
        if (this.y > rockbottom) {
            this.y = rockbottom;
            this.gravitySpeed = -(this.gravitySpeed * this.bounce);
        }
    }
}
function updateGameArea() {
    myGameArea.clear();
    myGamePiece.newPos();
    myGamePiece.update();
}
</script>


</body>
</html>

He probado diferentes cosas pero o me va...
Os dejo el codigo que he hecho hasta ahora

Código:

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<style>
canvas {
    border:1px solid #d3d3d3;
    background-color: red;
}
</style>
</head>
<body onload="startGame()">
<script>


function startGame() {
    myGamePiece = new component(30, 30, 30, 0, 0);
    myGameArea.start();
	
}

var myGameArea = {
    canvas : document.createElement("canvas"),
    start : function() {
        this.canvas.width = 480;
        this.canvas.height = 270;
        this.context = this.canvas.getContext("2d");
        document.body.insertBefore(this.canvas, document.body.childNodes[0]);
        this.interval = setInterval(updateGameArea, 20);        
    },
    stop : function() {
        clearInterval(this.interval);
    },  
	
    clear function() {
  ctx.fillStyle = 'rgba(255, 255, 255, 0.3)';
  ctx.fillRect(0,0,canvas.width,canvas.height);
}
    }
}


function draw() {
  clear();
  ball.draw();
  ball.x += ball.vx;
  ball.y += ball.vy;

function component(width, height, radius, x, y, color) {
    this.type = type;
    this.width = width;
    this.height = height;
    this.x = x;
    this.y = y;    
    this.speedX = 1;
    this.speedY = 1;
	this.vx: 5,
	this.vy: 1,
	radius: 25,
  color: 'blue',
    this.gravity = 0.1;
    this.gravitySpeed = 0;
    this.bounce = 0.5;
    this.update = function() {
        ctx = myGameArea.context;
        ctx.fillStyle = color;
        ctx.fillRect(this.x, this.y, this.width, this.height);
    }
    this.newPos = function() {
        this.gravitySpeed += this.gravity;
        this.x += this.speedX;
        this.y += this.speedY + this.gravitySpeed;
        this.hitBottom();
		if(this.x > 450){
		this.speedX = -this.speedX;
		}
		if(this.x < 0){
		this.speedX = -this.speedX;
		}
		if(this.y < 0){
		this.x = x;
		this.y = y;    
		this.speedX = 2;
		this.speedY = 2; 
		this.speedX = 2;
		this.speedY = 2;    
		this.gravity = 0;
		this.gravitySpeed = 0.5;
		this.bounce = 5;		
		}
		
    }
		
    this.hitBottom = function() {
        var rockbottom = myGameArea.canvas.height - this.height;
        if (this.y > rockbottom) {
            this.y = rockbottom;
            this.gravitySpeed = -(this.gravitySpeed * this.bounce);
        }
    }
}

function updateGameArea() {
    myGameArea.clear();
    myGamePiece.newPos();
    myGamePiece.update();
}

</script>

</body>
</html>

Espero que me podaís ayudar