Not a terrible game. There are a few issues as far as the gameplay goes.
First the wall moves too quickly, I understand it's supposed to be fast paced but instead of moving in a large interval in a matter of seconds you could instead have it move in small intervals constantly and still gain the same effect.
Secondly the firing system is kind of slow compared to the wall moving. Plus not being able to fire while the wall is moving means an added difficulty that should just not be there.
Other than that I liked the aftertouch system. The graphics are well done and the sounds are nice. You could add some music to help get into the game, though.