public static boolean isCollision(Circle c1, Circle c2) {
		if (c1 == null || c2 == null) return false;

		int xDist = c1.x - c2.x;
		int yDist = c1.y - c2.y;
		int rSum = c1.r + c2.r;
		if (Math.pow(xDist, 2) + Math.pow(yDist, 2) <= Math.pow(rSum, 2)) {
			return true;
		}
		return false;
	}