running out and only one are way too similar
Here's a pair of concepts that are different enough to warrant them being separate categories:
1). You are, comparatively speaking, a small human working as a corporate hireling tasked with tracking and hunting down rogue mechanoids. You're equipped with a melee weapon that can parry all melee attacks (but you have to dodge all ranged ones) and it can strip metal plates exposing enemy's weakpoints. You're also equipped with a ranged weapon that discharges a strong EMP, capable of shutdowning any mechanoid you meet, but only if you hit the weakpoint. No mechanoid has its weakpoint exposed at the star of encounter so you have to engage in melee combat. The "twist" is that the ranged weapon can hold
only one charge per fight.
Theoretical boss rush mode, stylized as an underground gladiatorial arena, where your EMP cannon recharges with hits against a weakpoint after you kill an enemy. You still can have
only one ammo for that gun.
2). The game starts as a walking sim, you appear to be a child who's wandered into a seemingly abandoned castle, admiring its rooms and their contents. rooms have very mild platforming mechanics meant to slow you down. As soon as you enter your first room, a very distinct sound of the chains rustling happens, signifying that the castle's gate is closed (if you walk back, you see that it indeed is). Once you explored enough rooms or spent enough time inside the castle, the same distinct sound of chains can be heard again (there is no other similar sound to make this one significant). When the chain sound stops, the game becomes an outrun sequence, because the castle is haunted and now there's a shade hunting you. You cannot fight back, only escape. If the shade catches you, you must sacrifice one memory fragment of a room you explored in the first part of the game. If the sacrificed fragment contained a memory of a room you walked by without interacting with objects and\or taking time to admire the visuals, it only slows the monster down. But if a room was thoroughly (but not necessarily fully) explored, it stuns the monster, giving you extra time, or, if you're felling risky, interact with more objects on your way out.
So, essentially, the game is about
running out of the castle without
running out of memories about the castle.
Potential high score rankings based on the amount/quality of memories you kept, or how quickly after entering the second phase you escape.
After you first complete the escape sequence, you get a small cutscene of an unspecified adult human suddenly waking up after a nightmare.