A bit slow at the start but got interesting later on. Sadly I got stuck, wave would not end despite no enemy being on screen.
Other complaint I would have is that at the start of the game I don't have enough cash to by anything at the first one or 2 shop visits. This feels bad if I miss an item I want but have no chance of getting. Would suggest starting with some amount of cash or make wave 1 a bit more rewarding.