I really loved the music! I enjoyed the variety and the pace in the different sections. I just left the tab open to listen to the main menu music while writing this review :)
You have an iInteresting way to integrate a tower into your skill tree. I think I would have understood things a little more if there was a tutorial section where you clearly explain what clicking on a block does. It was unclear if everything I chose I lose for a turn and then get stronger the next? Also it was unclear when I got it back that it got stronger without reading through a lot of stats on the left. Maybe you could do a level up with stats on the character showing what grew, or highlight the specific stats that increased when you level up?
I got to level 6 and started seeing some lag, though by level 2 some of the enemies were not de-spawning and getting stuck on the map, so that might have contributed to some lag.