I just played the game with my girlfriend and we both had fun and a good laugh listening to the music, which fits surprisingly well, as the ships "waltz" around each other.
Simplicity can be so powerful!
The ship triangles could already become more transparent, the more they get hit, not just at the end, when the ship gets destroyed. This way the ships themself are their own life indicators. This would then also maybe raise the need for some kind of recovery powerup, which the players could fight for, specially the heavily wounded one.
Art style is consistent also in the menu and choice of font.
Not sure, but maybe the projectiles could also teleport to the opposite side, like the ships do and then despawn based on a lifetime instead. This way, shooting could become a bit more strategic, firing at the right angle.
Well done, and thank you for this local multiplayer fun.