Real fun shooter with a cool premise ^^
Though i gotta say the music absolutely steals the show here, you sure didn't include a sound test for nothing these tracks are killer, title and boss themes in particular for me :p
Spritework is also really nice, i like your various mech designs, including the little sound test animation where one's Dj - ing the tunes XD and i thought the sudden fleeing birds to indicate the boss approaching was a rad detail !
The only negative i'd say is that the pre made assets you chose for the backgrounds and explosions while looking good don't fit all that well with your own sprites, so if you continue this post jam you should totally make some of your tiles and effects to have everything be a bit more cohesive together.
Other than that i didn't have any particular issues here, and still what i said is more nitpicking than anything.
Cool game and it was really fun to play, well done to you both :)