it's a start
Just throwing in some music can greatly improve how your game is received. Also, The black cubes appear on screen as soon as you touch the previous one, which is kind of lame. I would suggest placing the X axis of possible spawn points for the black cubes up higher. If you do that, there will be some small wait before you see one again, and it looks nicer because the cubes fall into the frame as opposed to just showing up.
I do like the game though, it's very similar to a project I myself worked on, Zombie Marv. I think you should check it out, and see if it gives you any ideas. I would be more than happy to help you, if it does.