Team members
1 (Mossieur Patate)

Software used
Love2D (+ Denver), Pixilart, Tiled, Audacity

Use of the limitation
The main mechanic is how your dioxygen and heart rate control doors. They can also influence each other (inhalate), and you have various ways to control them (run, propel yourself up one storey, get hit by an enemy). (I have also incorporated the theme in two ways: the context is a submarine one, AND the levels are multi-layered.)

Cookies eaten
None. I ate cereals, biscuits, drank coffee, fruit juice, and quite some stuff, but NO cookies. You can still give me one.