Initialised by the routine at 87CA; incremented on each pass through the main loop by the routine at 89AD (which moves the game clock forward by a minute when the counter reaches 0); reset to zero by the routine at 9584 when Willy sticks his head down the toilet; and used by the routines at 93D1 (to cycle the colours of the items in the room), 9534 (to determine Maria's animation frame in Master Bedroom) and 959A (to determine the animation frame for the toilet in The Bathroom).