Skip to main content

Building a Sanity System: Coding Eternal Darkness

· 2 min read
Thang Le
Thang Le
Senior Lead Engineer

Sanity System

Attacking the Player, Not the Character​

In 2002, Eternal Darkness: Sanity's Requiem introduced "Sanity Effects" that didn't just affect the character—they targeted the player. From "deleting" save files to muting the TV, these meta-scares are legendary. Building a modern equivalent in C# for Unity requires a robust, modular architecture that can handle a wide variety of "hallucinations."

The Sanity Controller​

The core of the system is a centralized SanityManager. This class tracks a normalized value from 0 to 1 and fires events as the player crosses certain thresholds.

public class SanityManager : MonoBehaviour {
    public float Sanity { get; private set; }
    public UnityEvent<SanityLevel> OnSanityTierChanged;

    public void ModifySanity(float amount) {
        Sanity = Mathf.Clamp01(Sanity + amount);
        // Tier checking logic...
    }
}

Modular Hallucinations​

We don't want the SanityManager to know about every possible effect. Instead, we use a Command Pattern or a ScriptableObject-based Effect System.

  1. Visual Hallucinations: These are driven by Post-Processing. As sanity drops, we increase the intensity of a "Lens Distortion" or "Color Shift."
  2. Auditory Hallucinations: Using our Binaural audio system, we play "phantom sounds" (whispers, footsteps) behind the player that have no physical source in the world.
  3. Mechanical Hallucinations: These are the "meta" scares. In Unity, this might involve subtly changing the player's movement speed, reversing their input for a split second, or showing a "fake" loading screen.

The Risk of Frustration​

The golden rule of Sanity Systems is: Never break the game. A sanity effect that causes a real crash or a real loss of progress is a bug, not a feature. The goal is to make the player think the game is breaking.

For Lil Sis, we've refined this by ensuring that all sanity effects are strictly visual or auditory. We want to gaslight the player's senses, not their patience. By building a system where "hallucinations" are just another layer of the rendering and audio stack, we can create a deep, unsettling experience that feels like the world itself is coming apart at the seams.