The artwork is amazing! It's nice there's a whole scene witht he hero and villain explaining the game. The shooting and scoring works, but I figured out a strategy pretty quick that works every time: just press w to go up a big and then shoot down. The opposite guy will do the same and miss, and you can easily shoot him. So after a while it was not very fun anymore, just repeating the same inputs without any particular goal.
But I think the idea has potential, you could for example make the boss mirror you in different ways (literally horizontally or vertically mirrored), they could use obstacles, or bounce projectiles off walls.