I like the simplistic style and the movement was easy to nail.
I was able to finish it (I think), I got 26 crystals and killed all the enemies but there was no end screen. Flew around a while to see if I missed anything but couldn't figure out what to do.
Vertical screen made it quite hard to see where you're going but I guess that's part of the challenge.
It was enjoyable, I hope to see more!