Simple and satisfying. Feels good to learn the patterns of the enemies. Except those square jerks lol, they always confused me. Art is amazing, sounds are jammin'.
PS. I was grabbing only the middle upgrade (more power) and after 2-3 I basically never ran out of power and never saw any upgrade screens. Not that balance is critical here or anything, but I was wanting that visual upgrade and couldn't get the screen to do so lol.