Rotate the air ducts so one terrible rumor reaches every desk on the floor before anyone does real work.
Every turn takes four minutes, undo included; rescrambling costs twenty. Everyone leaves at 5 PM, so tell as many desks as you can. Tap a duct to turn it clockwise. Long-press (or right-click) to pin a tile you're sure of. Keyboard: arrows move, Space turns clockwise, Q counter-clockwise, L pins.