I've gotten to eight seconds left and no further. The giant skeletons are too hard to learn - having to play forty seconds between them if you do it perfectly makes it hard to find out basic things like "these things have three health what the heck" and "you can stand on the tiles their heads cover but die if they slash while you're above them" - and also, I'm just not fast enough at moving or slashing to keep them off the mage or the crystal. I'm convinced winning this, if possible, is at least partly luck-based.