This is a very interesting concept! For me, in the middle of the game, I had an epiphany when I realized that I can move around the 2D arena with W/S and dodge enemies and projectiles. It's very nice when a game makes the game feel smart :D
I want to praise the upgrades and the fact that the game is moderately difficult, providing a challenge, this is very good!
P.S. BIGGER SWORD - one love :D