Nice game, I really liked the gameplay (although yes, hold to fire would be much nicer). I think AI could be incorporated a bit more into the game instead of it being a random tower placed. My idea was that perhaps you could make a tower controlled by the ai for a short time, so it does more damage maybe and fires on its own. But overall, very simple and fun game.
I'd appreciate it if you tried my game if you have time: https://itch.io/jam/wowie-jam-4/rate/1663155