Amnesia: The Dark Descent is a first-person adventure game with survival horror elements. The player takes control of Daniel, who must navigate Brennenburg Castle while avoiding various dangers and solving puzzles. The gameplay retains the physical object interaction used in the Penumbra series, allowing for physics-based puzzles and interactions such as opening doors and fixing machinery. Smaller items can be stored in an inventory menu, while larger objects can be raised by holding down a mouse button and pushing or pulling the mouse. Objects such as doors or levers can be manipulated by using the mouse in a fashion that imitates moving the said object. The game’s difficulty level can be adjusted preceding its initiation, but cannot be readjusted once the game has begun.
In addition to a health indicator, Daniel’s sanity must be managed, centered around an “afraid of darkness” mechanic. According to designer Thomas Grip, “the idea was basically that the darkness itself should be an enemy.” Sanity is reduced by staying in the dark for too long, witnessing unsettling events or looking directly at monsters. Low sanity causes visual and auditory hallucinations and an increased chance of attracting monsters, while its complete depletion results in a temporary drop in mobility, or death in higher difficulties. Light sources help restore sanity, and if none are available, Daniel may use tinderboxes to ignite candles and torches or deploy an oil-burning lantern. However, the number of tinderboxes and the amount of oil available are both limited, even more so in higher difficulties.