The Night

You cannot leave the school at night. Your classroom is safe only while the lights are on.

Light is safety

A room is considered "lit" once its brightness passes 0.55 (on the game's internal 0–1 brightness scale). That threshold matters a lot:

• Bob will not spot you, chase you, or stay chasing you in a lit room — if you reach one while he's after you and he's more than a couple of metres away, he gives up and goes back to patrolling ("Bob turns away").
• Grump, before he has turned, physically cannot enter a room lit past 0.62 brightness. After he turns, ceiling lights only slow him down (to half speed) at night, and enough time spent under lights makes him retreat for a few seconds — the exact threshold rises with the night number, from about 4 seconds on night 1 up to roughly 10 seconds on later nights. Lights do not slow him at all once it's daytime.

Room brightness comes from ceiling fixtures (only lit if the generator is running and that room's lights are switched on) and from portable lights (glow sticks, night lights) which work independently of the generator. See The Generator & Power for exact brightness falloff.

Hiding

Full mechanics on the dedicated Hiding page. Certain furniture can be hidden in or under: some lockers, desks, teacher desks, cabinets, toy boxes, reading tables, pianos, bleachers, vaulting boxes, cafeteria tables, serving counters, kitchen counters, fridges, storage crates, bathroom stalls, nurse cots, Lost & Found bins, staff couches, a round table, and a few playground props. See Rooms & The School for which furniture in which room.

Hiding is quiet: entering a hiding spot only emits a small noise (0.18, versus 0.5 for a normal footstep), and while hidden your fear rate drops by 3 per second. You can hold right mouse button to peek out without leaving. Some lockers can be taped shut from the inside with duct tape (30 seconds of being un-openable) — useful if something is about to check.

If Bob personally saw you get into a hiding spot in the last 1.6 seconds, he goes straight to it and opens it (100% chance). Otherwise, if he's investigating a noise, he checks the nearest unchecked hiding spot with a chance of clamp(0.18 + night × 0.025, 0.18, 0.42) — about 18% on night 1, rising to a capped 42% by night ~10 (and further multiplied by 1.6 during an "Overtime" night, see Night Modifiers). If he doesn't find you, that spot is marked checked and he won't re-check it during that same investigation.

Once Grump has turned, if he ends up within about 4.2 units of someone hidden, he stops and camps outside the hiding spot for 7–12 seconds, breathing, and catches you if you come out (or if you're still hidden when he loses patience, he gives up on that hiding spot for a while and moves on to search elsewhere).

Noise carries

Every action makes a noise level from 0 (silent) to 1.6 (a scream). Approximate levels:

Bob hears within a radius of (7 + level × 16) × hearMult units (hearMult is 1.6 on an Overtime night, otherwise 1). Grump, once hunting, reacts to noise within 10 + level × 22 units, redirecting toward it. Sprinting and crying are the two most dangerous sounds you can make. On an Echoes night, every noise level in the table above is multiplied by ×1.35 before either of those radii are worked out — see Nights & Difficulty.

Fear and crying

Fear runs 0–100. At night it rises by (1 − room brightness) × 7.5 per second and falls by brightness × 5.5 per second, plus a further threat pressure × 16 per second when Bob or Grump are nearby and hunting/chasing. Hiding subtracts 3/sec; holding a teddy subtracts 5/sec; having your torch on subtracts 2.2/sec; being below 15% food adds 1.5/sec. During the day, fear instead drains at a flat 9/sec (plus threat pressure × 6/sec if something is actively after you).

Who can hurt you, and when

Bob is a threat from night 1 onward, in every difficulty. Grump does not hurt you at all until he has "turned" — see Bob the Janitor, Grump, and Nights & Difficulty for exactly when that happens.