Impressive work for a 3-day jam, both on the gameplay and the graphics! I had a lot of fun playing this game against the AI, did 3 skirmish games which I won - but the AI seemed decent enough at any rate.
The help screen is good to get started. There were some mechanics I did not fully grasp, like the "increase temperature by 2 when attacked" which seemed to be triggered in both directions, with no clear visual feedback that it was during an attack (seemed more like +2/-2 at start/end of turn. But overall, the game rules are simple to understand and they work well. I like that you need to balance your fire/ice creatures to be able to both destroy enemy creatures and deal a substantial deltaT of damage :)
I'd like to play more of this game, so I can only encourage you to keep working on it and build upon this nice idea with a more polished UI, enhanced AI and some more cards in the deck (though the current deck is pretty well balanced already). And then online multiplayer of course :P