Super cool, i really like the overworld map to choose your level, the level themselves are a bit hard cause the spawnrate is fast and can get you quickly overwhelmed if you're in an area with multiple spawners to deal with, however i feel this could be more due to the fact that you cant attack in a direction and stay in place, or aim and move independently, nothing major, but i feel this could help improve gameplay a bit.
Other than that small issue the game feels really well made, i like the pixel art and animation, i had fun battleing the dragon boss, the music is epic, and i like the humor :)