I read through the most recent devlogs before playing. I can agree that the font can be hard to read. You may want to look at adding a setting to allow using an alternative font. You can leave your chosen one in place as the default, but for those who still have trouble, swap it out for a more readable one.
The tutorial feels incomplete. I suppose it expects you to right click on everything to proceed through it, but it felt like there should be more. After playing the required card, I would add a message to right-click on cards to learn the rest of the rules, giving a clear sense that the tutorial ends there. I started clicking and dragging things around to see what would happen, and managed to make it through the fight with only 1 card left on the board, with only its rune left. I had left clicked on the crystal early, which then felt like a waste as I figured things out and found it could only be used once. I really should have done more right-clicking sooner, but was initially looking to trigger the next tutorial step as it just felt like there would be more. Right-clicking on the cards, they do a good job of explaining things.
The game was challenging, and certainly had a bit of luck involved, but was overall enjoyable. I made it to the last fight before the boss of the second chapter, dying to the last few cards I had not been able to defeat. I'd had several bad streaks of many low number cards coming out early when the enemy cards were all high, and my HP was low enough I had no expectation of surviving the boss fight, even if I made it there. Reaching the new chapter and then getting a new deck was a bit unpleasant, especially when it felt like the enemies were getting more powerful and your deck was weaker than it had been. I also questioned from the description if your special ability was 3 times per fight, or in total for the chapter, as it sounded like there were only 3 in total.
I think that once you learn the symbols, the cards are fairly clear and easy to understand. The overall mechanics are pretty simple to understand, once you play a bit. The strategy, though, can take practice. This feels like a good core.