The Gun is Not Good. False advertisement, scam, refunded, etc.
Jokes aside - very polished. Some mechanics surprised me, like being able to dig. Shield gun is curious, it started growing on me mid-playthrough (not enough to start using it more though). Lazer, my beloved.
UI is great, combat is great. Nuclear Throne meets Crimsonland? Good stuff. I don't know what else to say, it's very polished.