I liked it! It was well designed in that I liked the art and I could understand what I needed to do just through the design, but it was a little *too* simplistic, once you've done the first puzzle, the rest are pretty much the same.
My only nitpick is that I couldn't hear the music! Maybe it's just a problem with my computer, so I'm not gonna give you a hard time about that. And I guess it fits the theme since you're only pressing one key at a time?