When waves start, even if I have an engine, I can't move around. I have to shoot or mash a few keys first then I can move. And in those initial seconds I might take some bad damage.
Also I don't see anything showing my money.... so I just buy modules until suddenly I can't. Which is weird. Why not show the money?
Also the art for the modules is weird. It should have transparent backgrounds instead of just white tiles.
Also the explosion sound is way too loud compared to the rest of the game's noises.
Finally, since this game is taken from Upgrade Complete's ship upgrading system, it would be nice if you'd mention it in the Author comments and in the game. (both not just one or the other)