Nice twist on an old concept. I like how the game becomes increasingly difficult, but not to the extent that it becomes impossible to beat. Although the gameplay itself isn't the most innovative thing, it works well, even though it's fairly simple.
The music is nice, and even though it is the same all the time, it doesn't really bore the player, which is a good thing. The rest of the sound effects are simple, but they suffice.
Perhaps it would've been a good idea to implement some kind of achievement system, to keep the player motivated.
All in all, a good game. 7/10