Mangle makes her way through the vent. However, once she reaches the vent to your office, she will never leave, and will enter your office the moment the vent door opens. The only way to stop her is to use the vent snare, which can only be active in one place at a time, forcing you to keep track of Mangle's location in the vent's to ensure that the correct vent snare is active. Once in your office, Mangle will hang from the ceiling creating audio disturbances before eventually dropping down to jumpscare you.

Nothing has changed. (Depending on AIs) but now in the game, the vent has a camera.