I liked it, for me the space was small and you could go out of borders

Overall this could be very nice, just needs more polishing and balancing - for example, the player speed, time between firing bullets number of enemies, etc. I noticed that there is no invincibility timer, which meant you're hurt every frame you're colliding with a card - kind of ruins the sound effect. Same with your attacks, if they come out every frame then the sound plays every frame, and it usually just sounds bad.

Good job !