From Wikipedia
Call of Cthulhu: Dark Corners of the Earth is a Lovecraftian horror first-person action-adventure game developed by Headfirst Productions and published by Bethesda Softworks in 2005, in conjunction with 2K Games.
The game is based on the works of H. P. Lovecraft, author of The Call of Cthulhu and progenitor of the Cthulhu Mythos. It is effectively a re-imagining of Lovecraft's story The Shadow Over Innsmouth (though diverging from the story in several places, and featuring a different protagonist, several levels in the game mirror passages from the story). There is also a sub-plot inspired by Lovecraft's story The Shadow Out of Time. Further, many scenes and major events were directly taken from the Chaosium Call of Cthulhu role-playing game campaign "Escape from Innsmouth."
The game has often been noted for featuring no HUD. The player character's condition is relayed through the sound cues of his heartbeat and breathing, which become more pronounced when wounded, and color draining from the screen with loss of blood and strength. Specific injuries are also indicated visually and aurally - a broken leg will cause Jack to limp and will make appropriate noises, a broken arm will make aiming more difficult, etc.
Jack loses sanity when he looks directly at upsetting aspects of the game world, such as mutilated bodies or precipitous drops... Sanity loss can lead to hallucinations and visions, which manifest as graphical anomalies, sound distortion, and changes in control sensitivity. Also, Jack will begin to suffer from schizophrenia, hearing voices from various sources, such as his inner child pleading for him to go back to darker personalities that want him to come back with them. If he is sufficiently disturbed, then permanent insanity or suicide will result and the game will end. The health system was designed as a more realistic take on character injury than other games of its genre in that different forms of injury will require different remedies, such as a splint for a broken leg.
Initially, the gameplay mostly comprises unarmed escape and evasion, together with investigative exploration, although weapons and combat are introduced later on. As with most survival horror action/adventure games, ammunition is limited and must be conserved carefully for situations when it will really be indispensable, occasionally requiring the player to avoid combat, even when armed. The game as a whole is heavily scripted and extremely linear, with only one path through the chapters from start to finish...