The ding sound is a bit sharp imo. Anywho, a fellow card game, how nice! Some cool concepts here and the potential for some serious depth. Though, I ran into a lot of rounds where neither me nor the opponent achieved anything at all. There are quite a few combos that just don't do anything, so I ended up just skipping rounds over and over again :/ But that's a balancing issue, can't really be too mad about that, with the 48h thing and all. Oh, also, an undo button would be nice :P
Good job overall. It's one of those games that makes you wonder how much farther the concept could go!