class App { 
	constructor( canvasId ) {
		this.cc = document.getElementById( canvasId ).getContext( "2d" );
		this.cc.tmp = new Object();
		this.cc.tmp.width = this.cc.canvas.width;
		this.cc.tmp.height = this.cc.canvas.height;
	}
	start() {
		this.timerId = setInterval( this.frame.bind( this ), 100 );
	}
	stop() {
		clearInterval( this.timerId );
	}
	frame() {
		this.draw( this.cc );
	}
	draw( cc ) {
		cc.fillStyle = "gray";
		cc.fillRect( 0, 0, cc.tmp.width, cc.tmp.height );
		cc.beginPath();
		cc.arc( cc.tmp.width / 2, cc.tmp.height / 2, 100, 0, 6.28, false );
		cc.closePath();
		cc.stroke();
		
		cc.beginPath();
		cc.moveTo( 0, 0 );
		cc.lineTo( cc.tmp.width, cc.tmp.height );
		cc.closePath();
		cc.stroke();
		
	}
}