A really nice game loop! :)
I can certainly see possible improvements like adding particles, screen shaking, lighting effects and more challenging elements as the score increases, such as larger rectangles, a faster ball, more ball or the player starts controlling the ball and has to destroy rectangles to increase his score, like the game is constantly reversing the game concept :D . You've got a simple but very effective concept and you can certainly make it an even more engaging game. Keep up the good work :)