itch.io

selecting a new tower from the bottom UI and placing it on top of an already existing tower, sell the old tower, build the new one. That would be the order I imagine it should work. And yeah, moving the towers could also be really useful here, something like: right click to pick it up -> attached to mouse position -> release mouse  -> place tower if tile available/ return tower to old position if tile invalid/ swap position if tile is another tower. I rambled too much here, I hope it makes sense.