I liked the idea that whatever the upgrades I didn't select will be applied to the enemies in the next waves. That's actually pretty clever! I think it'd have been cooler if I can pick and choose which one, not randomly select the "?" card.
Also a small thing but it'd be much more comfortable playing if my turtle is not at the centre of the screen. I was often unable to see far enough so I was cornered easily.
But overall, it's a neat little game that the turtle is just surviving and mutating in such a hostile environment!