Interesting upgrade system!
I liked the xp and card system, it makes replaying a bit different each time.
The enemies are a bit hard to see as they don't contrast a lot with the background + they are really small. This makes the game very hard as I took damages that I could have avoided if I had better seen the enemies.
I would have like to get an upgrade that gives more munitions, or more shooting rate, as the arena becomes more and more flooded by enemies haha! Maybe it exists and I just didn't get lucky!
Overall I enjoyed the game, even if I could not beat it! The death animation was a funny surprise haha!