Cytadela
An old-school first person shooter from classic Amiga computers
A conversion of an Amiga first person shooter from 1990's. Some say it's a Doom clone, but some argue that it's a Wolf 3D clone.
The Citadel is a secret military research base located on a distant planet. After the contact with the base has been lost, a military spaceship has been sent there with a mission to either restore the communication or, if that's impossible, destroy the base.