Hey, it was my first time playing your game. I tested on linux.
Right of the bat I am going to say I wish the game was turned based, but I see you are trying to make something different.
Your tutorial was good, except I didn't always know where I needed to be looking.
The "scrap" was confusing at first. I think "scrap" in deckbuilding games is something that would be bad for you, not good. Something like "useless cards that keep cluttering your deck".
Even with the game being real time, I think it would be much easier if you were able to use mouse to play cards., while still moving with keyboard.
I found the game very hard, so I am definitely not the target audience, but I kept trying. I wanted to get to the first boss without dying, but it always ended in failure for me.
After about 10 runs, I decided to use your demo option, and kept on going. I got to the first boss after 2 deaths, and surprisingly I found the boss to be much easier than the rest of the game (I think I was only hit once).
I am all for hard games, and yours kept me trying, so I can see how people who are into the genre are going to really learn all the combos, and strategies for dealing with different enemy types.