Fun little game for as quickly as it was made!  It's a nice touch that you get to choose your difficulty at the end, although if you're gunning for hard it looks like you have to specifically be building your deck around it, with a few self-sacrificing cards that clear the board to let you play more than five, and a decent engine that gets you to round 13 without any unexpected losses.  The random nature of sacrifice is rough, but turns playing the odds into part of the overall strategy.  Thank you!