eyeofmidas.com/htdocs/js/starfieldgame.js

function StarfieldGame() {
	var container = null;
	var canvas = null;
	var contextType = '2d';
	var contextAttributes = {};
	var context = null;

	var game = null;
	var starfields = [];
	var velocity = { x: -1, y: -1 };


	this.create = function (elementName, mouseBind) {
		game = this;
		container = document.getElementById(elementName);
		canvas = container.getElementsByTagName('canvas')[0];
		window.addEventListener('resize', game.handleResize);
		window.addEventListener('mousemove', game.handleMouseMove);
		window.requestAnimationFrame(game.handleRequestAnimationFrame);
		this.handleResize(null);
	};


	this.handleResize = function (event) {
		canvas.width = container.offsetWidth;
		canvas.height = container.offsetHeight;
		context = canvas.getContext(contextType, contextAttributes);
		context.translate(0.5, 0.5);
		game.init(canvas);
	}

	this.handleRequestAnimationFrame = function (event) {
		game.update(canvas);
		context.fillStyle = "#000000";
		context.fillRect(0, 0, canvas.width, canvas.height);
		game.draw(context);
		window.requestAnimationFrame(game.handleRequestAnimationFrame);
	}


	this.handleMouseMove = function (event) {
		//game.mouseMove(canvas, event.offsetX, event.offsetY);
		game.mouseMove(canvas, event.clientX, event.clientY);

		let canvasBounds = canvas.getBoundingClientRect();
		if (event.clientX < canvasBounds.x ||
			event.clientX > canvasBounds.x + canvasBounds.width ||
			event.clientY < canvasBounds.y ||
			event.clientY > canvasBounds.y + canvasBounds.height) {
			game.mouseMove(canvas, canvas.width / 2, event.clientY = canvas.height / 2);
			return;
		}

		game.mouseMove(canvas, event.clientX, event.clientY);
	}

	this.init = function (canvas) {
		starfields = [];
		for (var i = 0; i < 3; i++) {
			starfields.push(new Starfield());
		}

		for (var i = 0, starfield = starfields[0]; starfield = starfields[i]; i++) {
			starfield.init(canvas, i + 1, velocity);
		}
	};
	this.update = function (canvas) {
		for (var i = 0, starfield = starfields[0]; starfield = starfields[i]; i++) {
			starfield.update(canvas);
		}
	};
	this.draw = function (context) {

		for (var i = 0, starfield = starfields[0]; starfield = starfields[i]; i++) {
			starfield.draw(context);
		}
	};

	this.mouseMove = function (canvas, x, y) {
		for (var i = 0, starfield = starfields[0]; starfield = starfields[i]; i++) {
			starfield.mouseMove(canvas, x, y);
		}
	};
}