Thanks for the feedback and I'm glad you enjoyed the game. I do agree with your comments.
The walls were created really early and I didn't know how else to really change them. A lot of small changes could help and really change the experience. Like adding to the economy or getting some resources from enemies, so you could place more buildings down. A slow zone would be pretty nice, I'll keep that in mind. I do wish to improve upon this but I think I'd start a new project for that instead of modding this one. I had a vision for this project and didn't want to change it too much and get lost in a random direction and not complete the game.
Yeah, I need to study into making a better target acquisition method. Right now, there is a large collider around it and an OnCollisionStay but this is pulled for every Enemy within the collider and can mess it up. I have a button to try to null out the enemy that it's targeting but I wasn't able to get it to work right. Sometimes it would retarget and other times it would retarget the same enemy. I'm not sure what code would cost the cheapest, if creating an array of enemies within the collider and then measuring distance to each and going off that would be too costly or not.