Create gameplay with first person shooter game in dark fantasy theme in 48 hours with a level-based structure and an emphasis on finding the proper keys to progress. The theme is "Dungeon". 

Styles & References:

Heretic is a dark fantasy first-person shooter video game released in 1994. It was developed by Raven Software and published by id Software through GT Interactive.

Hexen: Beyond Heretic is a fantasy first-person shooter video game developed by Raven Software and published by id Software through GT Interactive Software on October 30, 1995. It is the sequel to 1994's Heretic, and the second game in Raven Software's "Serpent Riders" trilogy, which culminated with Hexen II. The title comes from the German noun Hexen, which means "witches", and/or the verb hexen, which means "to cast a spell". Game producer John Romero stated that a third, unreleased game in this series was to be called Hecatomb.

Rules:

• You can use pre-made examples, but not a full game. E.g. you could use Unreal Engine 4's FPS template of Unity Game Engine, but you must change all of the assets for your own. You cannot use a game you've previously made and just build upon it. You can make it all from scratch if you so desire.
• You can use your own assets or commercially free-to-use assets.
• No NSFW/nudity of any kind. If that's your thing, you must not enter.
• No insulting content (e.g. swearing, blasphemy, extreme gore, etc.).