If you plan on expanding the idea into a full game:
* Add a "map" (folder tree, that is) so we can better find our way through.
* In relation to that, an item that when acquired allows the player to skip to any previously folder by clicking it on the tree.
* Add alternatives to overheat consequence (like a thief who may crawl through the folders to try to steal your items, or a reaper that warps through folders every two moves and cannot be killed on top of dealing a lot of damage if you don't leave the folder right away...)
* Endless mode, of course!
* Classes system with different perks
* A Virus boss that lets its presence be known in the floor by spawning "corrupted files" that hides the identity of the real enemy it's supposed to be.