public Set<Light> updateLights(int[][] board) {
		
		Random r = new Random();

		for (Light l : lights) {
			MoveableLight ml = (MoveableLight)l;

			// randomly move it in one direction
			// these methods return true if the move is allowed, false otherwise
			// a move is not allowed if it would go beyond the world boundaries
			// you can get the light's position with getX() and getY()
			switch (r.nextInt(4)) {
			case 0: ml.moveUp(); break;
			case 1: ml.moveDown(); break;
			case 2: ml.moveLeft(); break;
			case 3: ml.moveRight(); break;
			}

			// randomly turn the light off or on
			// you don't have to call these each time, of course: a light that's on stays on
			// you can query the state of the light with the isOn() method
			if (r.nextInt(2) == 0) ml.turnOff();
			else ml.turnOn();
		}
		
		return lights;
	}