My suggestions:
- Blind drops onto spikes usually doesn't feel good to the player, because they can't see. It can be done right but its tricky. Try to minimize these.
- At the start because there is no walk animation and the ground is solid color, it takes a while to realize you are moving. Try putting a single tile in the start location, so the player can see themselves move relative to it on the first screen.
Like the other commenter said, focus on puzzles that involve switching the temperature to get through.