I really enjoyed this game. Once you get a good run going, it is very fun.
There are some things that you could improve on if you want to, based on my experience.
-Some runs are dead in the early-game because of RNG
-The early game, starting with wave 3, has a major spike in difficulty that then linearly increases.
In my opinion, the ideal difficulty curve for a tower defense is exponential. This difficulty curve looks more like this graph I drew. The graph is my subjective experience playing the game, but it is grounded in actual gameplay experiences.