I couldn't get the spikes/pistons to actually place. I definitely had enough money for them, and they'd show up on my cursor but clicking or pressing the button again didn't put them down. Cool idea! You're definitely cementing yourself as the tower defense guy in my head, lol.
Respect for the ambition on this one, and the actual combat was surprisingly solid. Some knockback would have added a ton of strategy to the combat element - choosing whether to try and slow down certain mobs with knockback or DPS down weak mobs, or whatever. I'll give your updated version a try after I rate all the other submissions.
Well done!