In Five Nights at Freddy's (Scott Cawthon, 2014) the man on the phone says the characters are left in "some kind of free roaming mode at night". It feels like being hunted. You never see one walk: the feed cuts out and it's in another room. Players built theories. Stare at Foxy too long and he gets mad. Sit still in a blackout and Freddy waits. Neither is true.

Players who took the game's code apart found a die. Tech Rules read the decompiled project in 2020: every few seconds (3.02 s for Freddy, about 5 s for the others) the game picks a number from 1 to 20 for each animatronic, and if its level meets that number, it moves. Level 0 never moves, level 20 always does. Night one starts all four at 0, so nothing can move until 2 a.m., when Bonnie gains a level. The 0 to 20 on the Custom Night screen is that same level.

Two of them really do wait for you to look away: with the camera up, Freddy and Foxy fail every roll. Once Freddy reaches the corner by your door, he plays by other rules.

This rule comes from fans reading the game's code, not from Scott Cawthon. The restaurant, the robots and the rolls are our own simplified version, run in code.

Did you ever beat all four at twenty?

Sources: the game's own phone call and Custom Night, 2014; Tech Rules, "Ruining FNaF by Dissecting the Animatronics' AI", 2020; jerakaigamez, "Dissecting The AI Of FNAF 1".
Sounds and music: our own, made in code.
Unofficial. Not affiliated with or endorsed by Scott Cawthon. Five Nights at Freddy's is a trademark of its owner.