I love the twist on the turn-based battle, turning it into more of a puzzle. It always feels good to put a clever combo together! It's a shame the prototype doesn't really showcase the idea that you can only use a spell once... but the one turn aspect is still enough to carry it.
My only suggestion would be a bit more information in the UI - it feels a bit cheeky (oh no, Mark's rubbing off on me) not to tell the player what the monster will do on its turn when it can kill you in one turn if you don't prepare properly - and it was tough to remember which spell did what in the battle screen.