The art is really beautiful, gives a great retro vibe. The temperature mechanic is interesting in theory, the problem is that in reality it is easy to kill the enemies at any temperature. I think making the difference between hot and cold more pronounced would help a lot, changing enemy behavior depending on temperature could also be an interesting way to approach it.
I also found the game UI a little obtrusive, especially when walking upward. Just reducing the size would probably help a lot.
Overall, good job!