Five Nights at Freddy's 2

Five Nights at Freddy's 2 removes the doors that defined the first game entirely, there's nothing physically blocking an animatronic from walking into your office, which forces a completely different defense: put on a Freddy mask and hope whatever's standing in front of you mistakes you for one of its own.

The music box adds a second countdown running alongside everything else, letting it wind down invites out a threat from the vents that the mask alone can't stop, so checking in on it regularly between camera sweeps matters as much as watching the hallway itself. Because the mask doesn't fool every animatronic in every situation, learning which threats need the mask versus which need a direct camera check is the real skill the game is testing over its five nights. Five Nights at Freddy's 3 swaps the mask for hiding and system reboots in the next entry.