After significant work, Rewolf was given some office space, funding and a mapper (Jeff Lane) by Valve Software to help complete the project,[2] and it was released as a standalone game.

Gunman Chronicles is a first-person shooter that requires the player to perform combat tasks and puzzle solving to advance through the game, much like its predecessor Half-Life.

While gameplay is similar to Half-Life's in terms of health-and-armor systems and artificial intelligence, one major aspect of Gunman Chronicles is the ability to customize each weapon.

The game features a wide variety of enemies, including rogue Gunmen-turned-bandits, giant dinosaurs, genetically-modified aliens called Xenomes, and robotic attack drones.

[citation needed] According to the game's introductory cutscene, the Gunmen act as a sort of military police force for humanity's inter-galactically expanding colonial empire at an unknown time period in the distant future.

During a mission five years prior to the beginning of the game, the Gunmen were dispatched to a planet called Banzure Prime to investigate a communications breakdown with a research colony there, under the command of their leader, known simply as "The General".

The General, seeing his men have no chance by themselves, takes command of one of the Gunmen's dropships and begins performing bombing runs on the attacking Xenomes, destroying several before being captured in the jaws of one of the larger creatures.

Five years later, the game places the player in direct control of Major Archer, preparing for a mission aboard the Gunman space station Aeronautica.

After a training level, Archer and a small detachment of Gunmen are deployed to a dinosaur-inhabited jungle planet, under orders to investigate an outdated but extremely high ranking Gunman distress signal.

Major Archer and the AI successfully reach and board the aerial drone, but fail to navigate through an asteroid field on their way into kata-space and crash land on a desert planet called Icnus, encountering and fighting rogue Gunmen.