Initial gameplay of Call of Cthulhu: Dark Corners of the Earth comprises unarmed escape and evasion together with investigative exploration, althoughfirst-person shooter (FPS) style combat is introduced later on. As with mostsurvival horror video 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 very linear, with only one path through the chapters from start to finish, in contrast with some earlier survival horror games such as the original Alone in the Dark (which itself was inspired by the Mythos).
The game features no heads-up display. Instead, condition of the player character 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: for example, a broken leg causes the character to limp while making appropriate noises, while a broken arm makes aiming more difficult. The health system was designed as a more realistic take on character injury than other games of its genre in that different wounds, including poisoning and bleeding,[2] require different remedies, such as a splint for a broken leg.[3] The inventory screen shows the character's injuries (displayed on his character model) and all carried items.
The player's character gradually loses sanity when he looks directly at upsetting aspects of the game world. The character's mental degradation can lead him to hearing hallucinations and visions, which manifest as graphical anomalies and sound distortion, and changes in control sensitivity. If the character becomes too unsettled, results may include his permanent insanity or suicide, and a game over.[2] The sanity can be restored through finding areas of sanctuary or defeating enemies.[2] The areas marked with the Elder Signs serve as sanctuaries against the enemies and as save points.[3] To enhance its replayability value, the game features a system whereby players can gain Mythos Points, supposed to reflect a level of gained knowledge. Such points can be used to unlock in-game bonuses, such as additional information and items.[2]
Most of the ranged weapons are based on real firearms with the exception of a Yithian directed-energy weapon introduced at the end of the game. The player character can also perform a melee attack with a crowbar or with a gun if all ammunition for it has been used up. The game features a realistic combat system: due to lack of HUD, the player has to count shots manually to know when the gun goes empty. There is also no artificial on-screen targeting reticle; instead, the player must aim through the iron sights on the weapons themselves, but sustained aiming tires the character and drops accuracy. The shooting system is unique in that fired rounds go exactly where the gun's barrel is pointing. For example, if the player character readies a reloaded weapon and the player pulls the trigger before the character animation has finished, the round will be discharged in the direction the gun was pointing when the shot was fired.
