Ok so I got a solution to what can happen to the extra heat that is wasted at the end of each level. I do not know if it has been suggested before, but I will post anyways. So what if players can buy a tank that is used to store the extra heat? It's pretty self explanatory, the heat tank, as it can be called, is used to hold the extra heat that is left over from each level we explore. This heat tank works in the same way as the energy tanks in the Megaman X series, where if you have full health, the energy tanks fills up with each extra health you pick up. So here's my idea. Enjoy.
yes this has been suggested some have said that heat tanks should be sold others have suggested that the heat should be used to craft materials and the like