Some towers are supposedly better against certain enemies. Arbalet does damage that can only oneshot red enemies, Catapult and MagicCircle do enough to one shot both grey and black.
Spears were meant to only be able to kill reds and get damage from everyone else. But I made that there is a push back when an enemy is attacked. So that made the Spears to be able to kill everything. And I was too chill to overwork to fix it.
I hope that you liked the concept. I think with a twist like having it as a classical tower defence, but with the option to drag the towers and aim with them during the waves... It might turn out lit...