Hey Philipp,

I played your game and I think there is a lot of potential. However there also were a bunch of problems I encountered in the current version so far. I seperated the problems out and gave a short facit at the end. I hope it helps you. Keep it up, you made something pretty cool!

UI / UX Problems:

1.1.) I didn't know immediately that you can take the spheres out of the cards, I found that out after selling a few cards which had spheres inside.

1.2.) I didn't check if the selling price of a creature you have is different based on the spheres you have in, but I think it should be

1.3.) I didn't know that you can sell only a single card, It was unclear to me that this limit existed

1.4.) You don't see your deck when you choose a reward, which makes it sometimes hard to remember what you already have

1.5.) You cannot resort your own cards when you're looking at your deck.

Potential balancing / Game design issues

2.1.) The usefulness of the white gems is unbalanced. The "when card attacks" is generally the best one, as it triggers always reliably. Some card e.g. "when taking first time damage" on the other hand only trigger once and are therefore way worse. Since there is no cost difference, this feels heavily unbalanced

2.2) It seemed to me that it is rather easy to build what is known as a "generator". Generators are cards which create something out of thin air and lead to an infinite combo. i haven't tested most combinations.
I played to the first boss and build myself a card, which was "when creature attacks apply poision(4) and shield(3), which was already grossly overpowered.
But the amount of combos you can string together seems insane, however following them when they play out i also difficult. Especially since cards can have up to 5 effects, and when an eneemy attacks you (in the bossfight) stuff happened so quickly that i had a hard time following what was going on.

2.3) the map where each hex holds 4 options seems weird. I dunno why one option wouldn't cover 1 hex and you you just make the hexes smaller. You anyways don't see which options there are until you are close by, so also long-term strategizing seems not possible. Deciding for any path is arbitrary, as you just take the combos which suits you bette,r nad it#s always a bad idea to go to the borders of the map, as the option space there is severely limited.

Facit:
The game feels really polished, all the effects with taking cards, moving them around etc. feel really polished and well done. Also the mainscreen art is cool. The soundtrack also works for the game and is not too upfront but also not to subdued.
I think that the main problem right now is the option-space design, as it's quite easy to build super op combos rather quickly, and because there are so many unbalanced options, choosing the best is usually a clear decision and not an interesting one.
With more work this could indeed get quite interesting. It's not there yet, but has in my eyes a lot of potential.