This reminds me a lot of Devilition from UFO 50, in a good way.
Took me a few minutes to understand (to an extent) the gameplay, and stop hitting the top-right button which apparently resets the game :) Not sure if there was supposed to be an icon there, and on the other squares in the corners.
I didn’t understand what the popups at the bottom with board layouts were trying to tell me.
The difficulty also needs some tuning, I stopped after 25 marks because the board was full of monsters but somehow I still kept getting back to full health every turn. But I had fun!