UI and Music are nice, upgrades are cool though sometimes you can get 2 of the same. IMHO the only issue I saw was movement, which feels not as responsive in the beginning as it could have been.
The game is quite enjoyable, I rarely play for half an hour without noticing that I am playing. Ballance is nice, controls are exactly as precise as they should be.
UI/UX is a mess, i.e. it is quite hard to figure out what to do in the beginning and later the extra steps slow down the game. Edits to that should make it way more enjoyable. The visuals are nice.