Awesome
That was pretty good, man. Just hard enough not to be easy, but simple enough to not make me want to throw my computer against my brother's head. In retrospect, it can become a very addictive game; you've managed to create something very good out of a simple idea and make it into something fun and challenging at the same time.
The ability to change the background was a nice bonus too, right along with the two seperate styles of gameplay (and although they use the same levels) they provide a fresh experence after playing through one style for awhile.
My only probem is the sound, which probably would have gotten annoying if i wern't so used to just listening beyond (so to speak) sounds and music in video games.
All in all, a very impressive piece of work there. You could probably make a few more games of these and keep people coming back for more. I could actually see this selling on a game site or something. At any rate, keep up the good work, sir.