Following the events of the Uwe Boll film of the same name - which itself was not based on an existing video game - you play a soldier on a mission to locate members of the original "Tunnel Rat" squad from the film. To this end, you must make your way through a series of sparsely decorated Vietnamese bases and - as the title would imply - tunnel systems filled with a small variety of recycled traps.
Along the way, you are meant to collect the dog tags of your fallen comrades, as well as "trophies" from the corpses of your foes (Their severed ears). By collecting these, your health bar eventually increases in size, allowing you to survive more damage from enemy soldiers and from the grenade traps. The majority of traps are instantly lethal, and must be defused / disabled before progressing further.
As you kill enemies and inspect tunnel traps, the player character's inner monologue provides insight into his madness. Whereas the stories of some games might document a character's descent into madness, the main character of Tunnel Rats seems to have been a psychopath for some time now, displaying no remorse for killing his enemies and seeming to feign sympathy for his dead allies.
The game was received unanimously poorly by critics, with it's metascore currently sitting at "30." Common complaints include the blandness of the graphics and level design, the tedium of the combat and tunnel crawls, and the silliness of the player character's inner monologue.