While the gameplay was fairly good, there were some definite problems.
#1 - Way to easy. Like, seriously, it was one of the easiest games I've ever played.
#2 - Hit Windows. The enemies occupy vague spaces, which is fine, of course, but the spaces are too large, and they hit you when they shouldn't. Especially the final boss' tail attack, which I was nowhere near when I was hit by it.
#3 - Sound. Seemed a little lackluster. There doesn't seem to be a hit sound effect when you're struck by an enemy.