Interesting idea. As defeating enemies deals damage to you as well it leads to more tactical playing. I think it would be beneficial to have some kind of feedback when you deal damage or have card drops independent to defeating enemies to have more variety to the game. On the third try something weird happened and all the objects started to go up

It would be nice if I could receive cards more often.

I don't really get it. I managed to get to 5 cards once but usually I can't get past the first two. The first ones seem to take 3 hits to kill but the ones after that seem to require more hits than you yourself hand handle. You could theoretically pre damage before some enemy before using a card to heal you but even killing an enemy without getting the card is way too tough. The slowly moving AI makes all the enemies clump up in a single cluster pretty soon making it impossible to target single enemies. And the lack of any indication of health left on self or enemies makes it even harder.

I keep going for more tries even while writing this but it seems weird. I just managed to kill one of the first two enemies without grabbing the card. Made two bumps on the third enemy, grabbed the card to fully heal and even by doing so I couldn't beat the third enemy. It just doesn't seem constant how much damage you do and how much damage the enemies do and how fast. Makes it rather frustrating to play.

There are also rare scenarios where an enemy bumps you and you go flying to the other direction losing all control for a bit.