This is a very nice bullet hell with an interesting twist! I love the idea of choosing both your upgrade and deciding how hard the enemy would be at the same time. Such an interesting twist and I am having fun! I also like the fact that each upgrade in the game feels strong enough to influence the game in a meaningful matter, like the damage upgrade really makes you hit harder, and you can really feel that enemies are dying faster. Another thing that I really like is that the game introduces elements in a slow and digestible manner. Well done on that!
For a bit of minor issues and suggestions, I'd say the heath pick up is too small. It's quite unnoticeable when you are focusing on fighting enemies and dodging bullets, and I would hope they are a lot more prominent in the scene. I also think the card-flipping animation is a bit too long, and looking at that for each level is quite time-consuming and flow-breaking. A skip button that flips all the cards would be very nice.
Anyway, this is a very nice game! I do like it a lot. Well done!
P.S. Here's my score
