Nevermind, I got confused thinking it was refferering to the upgrades, I didn't realize there was 3 towers you could choose from.
Anyway, the mechanic is quite fun, though the process of switching towers is a bit janky, its almost impossible to switch towers on the later waves (since you have to remove the tower, choose which one you want to place, place it and upgrade tower to full again), also sometimes I try to place a tower but it doesn't do anything, so an indicator for that would be cool.
I also found some bugs when retrying, it once restarted the game at wave 10 lol, and another time I started the wave but no enemies appeared.
but yea I like the concept, good job!
oh and maybe add a time slowdown when you remove a tower? (because the enemies at later waves just go at mach speed lol)
also you could make so that the first two towers always get placed with as many upgrades as possible (you won't really lose the money, and its not like you will use it anywhere else)
and perhaps make the freezing tower a fixed cost but its always fully upgraded? I say this because that tower is only really needed at later waves, and by that point you will need that tower fully upgraded anyway so you can slowdown all the enemies.
But anyway those are just some quality of life changes you could add later if you want..
