I think the concept of this game is cool, though I ended up feeling like the most effective way to play was to keep heat as low as possible, which felt like a shame. Maybe there’s a way to incentivize the player to balance heat at higher levels so they spend more time going faster?

Great job! Your game looks great, the idea is very unique and well implemented, I would never have thought in an idea like this. I would advice you to use the limitation directly in the unique gimmick or main mechanic of the game instead of just the player's mobility, just to make it stronger.