This Is Honestly A really Neat Idea, The problem? I first tried it, Very easily. The heat system is Really good, but I never felt too much under pressure from it. But Thats fine, As this really seems to only be there so you don't just Grab EVERYTHING from a dungeon. However, I could see this being a full fledged Replayable Game, With some extra stuff. Heres my list:

1. Endless mode, Self explanitory, Would add a bunch of replay value.

2. Hard Mode, Simple, Enemy health and damage scale way harder, and your heat limit could be lower.

3. More floors/items, A basically just add more content to the base game, thats it.

But seriously, This is an incredible game, and I Could see this being on store shelves and steams home page, Keep up the good work!