Once I understood how to sacrifice the cards (drag to right-most red card slot), I was cruising. Until I ran out of cards and lost. I enjoyed this a lot, and your custom track is dang good for a first track! Your art style is fun as well. I think my biggest critique is that the text is too small, even on fullscreen, to read well. Some basic instruction of what is where (where's mana? got it after a bit) will also really help. Very good marks from me!