Implemented the guard towers. They are upgradable and garrisonable. I still need to improve the system so that multiple guards can use them at the same time, but that won't be too hard. I love how easy it is to add new behaviors to the AI with the state machine I have written, it makes developement very fast and iterative.
I'm not sure how to orient the weapons of the guards yet, though, since it's all pixel art. I hope i don't have to do multiple frames for it.