Post
The invisible math that determines whether that guard actually saw you or you're just being paranoid.
Stealth detection systems simulate how enemies perceive the player through sight cones, sound propagation, light levels, and alert states. Most systems use a detection meter that fills as the player lingers in an enemy's awareness zone, giving you a window to react before full detection. Enemies typically cycle through unaware, suspicious, searching, and alert states. The design challenge is making detection feel fair and readable -- players need to understand the rules to play within them. Opaque detection leads to save-scumming; transparent detection enables planning and mastery.
Example
Metal Gear Solid V has one of the most sophisticated detection systems ever built. Enemies use realistic sight lines affected by lighting, weather, and even the direction they're facing. The reflex mode slow-motion on detection gives players one last chance to react. Hitman's social stealth adds disguise-based detection where different NPCs see through different disguises based on their role.
Why it matters
Stealth detection is the invisible contract between the game and the player: follow these rules and you're a ghost, break them and chaos erupts. When detection feels fair, stealth games are uniquely tense. When it feels random or unfair, the entire genre becomes an exercise in frustration and quicksaving.
Related concepts