Liked how all of the attacks are different. It was a bit easy though (just keep your fingers on the 4 keys) and you couldn’t do much else if it were harder. It was fun for a round though.
I tried to make waves 1-10 pretty easy, but if you beat the boss and continue in endless mode the difficulty should scale pretty quickly, if that's what you're into. Also, considering its the second most powerful weapon, I strongly suspected "U" would be a favorite, I'm glad to see I was right.