Really well made! The ship controls were smooth and it's a great-looking game. I found too that it was well optimized and I didn't really experience the lag that I normally do with 3D browser games.
It fit right into the sweet spot where each wave ramped up the challenge and I felt like I had time to try different units. Granted, I wished there was a tooltip to see what each one was/did, but it was something that explained itself as time went on.
My only suggestion would be for the later enemy units to stand out more. By wave 6, I didn't realize there was a new enemy type. I was flying around looking for asteroids thinking, "Huh, what's this cute sound?" And then I shot the thing making the cute sound and was like, "Oh, he's not one of my guys." LOL