Great job on using temperature and health as a mechanic - a very interesting choice, that worked very well! Having obstacles sometimes be useful to decreasing your temperature was a neat idea too, and it put an interesting spin on the typical platformer style. One thing I would say, though, is that the key temperature and your temperature being different was a little annoying, especially when having to go back to heat it up, and not being able to see the target temperature at the start made for a lot of backtracking and wasn't too fun. It was quite a challenging game too - though that's not a bad thing!
The artwork was very nice, and I especially loved the background. That giant skeleton is so ominous, and it looks so good! The lighting effects around the fire helped distinguish it from the rest of the level, which was helpful when looking for them from afar. The freezing animation on death was a idea, but it sometimes didn't properly work, namely when I jumped on a bat - why I was jumping on a bat in the first place, don't ask. The music was a good choice for the game, and the sound effects added a lot to it as well.
I always love a good story-driven platforming sort of game, and this is no exception! There are a lot of good ideas, so very well done for making this game!