Nice little game, but imho there is great window for diversity and improvement. I suggest looking into other popular TD maps (Element TD, Hell TD, Gem TD, etc.) and seek there for more variety in enemies and, maybe, towers too. There is also popular element of adding of "ally creeps" like in Kingdom Rush games and their clones. I dont know much about challenge of adding creeps in-fight in current version of game, but such layer of gameplay, like on-path traps and "beef blockers" could be used for great effect.
Thanks for the feedback buddy, it's very encouraging! You're absolutely right - there's still a lot of things you've described that haven't been implemented yet, I'm just finishing checking and testing all the basic game mechanics, and I'll start filling in the content soon) and there will be more towers and creeps).
Subscribe if interested, literally in the next few days will be a new update, where I will introduce a "special" type of towers with effects, which will be very different for each game race of towers, and some races such buildings will probably generate allied mobs).