Derelict is a first person shooter and a tactical action game inspired by Space Hulk: Vengeance of the Blood Angels. The player controls a group of 5 space marines in two ways: directly in first person view (with the keyboard and mouse) or by giving them orders via map view (primarily with the mouse). Each marine has its own skills and abilities:
- Communications: the communications specialist can see enemies in the map screen.
- Heavy Assault: carries a belt fed Gatlin Cannon which doesn't need to be reloaded.
- Demolition: the demolition expert carries a modified rifle with a grenade launcher attached, which power can rip apart obstacles and temporarily disrupt teleportation systems.
- Engineer: carries automated tools to repair doors and can hack security system faster than the other marines.
- Medic: can heal the other team members and has a hazard suit which allows him to walk through dangerous areas.
The game has a total of 20 levels and five difficulty ranks, from Private to General, and the harder the rank, the more frequently enemies respawn, the quicker they move and the slower the medic heals.