at least it pauses for you when you place a building. I don't like games that have this type of entity cramming, it's just unsatisfying and feels bad. i'd much rather have a hard limit to the number of towers and not have them jump around and pile on top of each other. Having no limit to the number of units is fine as long as you don't handle it this way. 

However, for a game jam, this is pretty, pretty good.