There's only 2 sections rn, we intended to have 3 in this one originally but ran out of time, so the 3rd will probably be in the next version. Ideally we'd have 4 in the end. when it comes to the progression into the later levels, the idea is that keeping your heat higher is more necessary as you go on, we'll probably make some changes to the 2nd area though so there's more warning for that kind of thing.
Viewing post in DownFall - TriJam #333.2 jam comments
Ah, I see! Well then I'm extra proud of my progress :)
If the entrance to the section always started with an orange barrier, then it would be a clear hint to the player to try to keep at least orange heat in the section. Though the introduction of orange minimum heat at the same time as portals and the zigzag tunnels might be a lot to add to a single section.