The card-combining mechanic is really cool but i don't think it works in practice. There's no real time to strategise (or even read what each spell does), so the only thing that works is to just spam as much stuff down as fast as possible. Maybe slow down time when looking at a card or something?
The art is well done, no complaints there.
I'd love to see a more refined version of this concept, because my actual gameplay experience was pretty mixed.