Initialised by the routine at 8912, checked by the routines at 8DD3 and 8FBC, and checked and updated by the routines at 8ED4 and 91BE. Possible values are:

Value	Meaning
0x00	Willy is not on the rope
0x03-0x20	Willy is on the rope, with the centre of his sprite anchored at this segment
0xF0-0xFF	Willy has just jumped or fallen off the rope