function WorldGen(game) {
	this.game = game;
	this.prevX = 0;

	this.minY = -400;
	this.maxY = 400;
	this.powerupCounter = randInt(WorldGen.range[0], WorldGen.range[1]);

	// Spawn player and background
	game.spawn(new Player(game));
	game.spawn(new Background(game));
}
WorldGen.range = [5, 12];

WorldGen.prototype.update = function() {
	while (this.game.camera.x + this.game.canvas.width > this.prevX)
		this.genNext();
}
WorldGen.prototype.genNext = function() {
	var x = this.prevX + 300;
	var y = Math.round((Math.random() - 0.5) * 300);

	if (y < this.minY) y = this.minY;
	if (y > this.maxY) y = this.maxY;

	var obstacle = new Obstacle(this.game, x, y);
	this.game.spawn(obstacle);

	this.prevX = x;

	if (--this.powerupCounter === 0) {
		var powerup = new PowerUp(
			this.game,
			x - 50,
			y + 80 + (this.game.canvas.height / 2));

		this.game.spawn(powerup);

		this.powerupCounter = randInt(WorldGen.range[0], WorldGen.range[1]);
	}
}