Used by the routines at SPAWN_CREATURE, CREATURE_UPDATE, MONSTER112_UPDATE, WANDERING_MONSTER, SPEED_BONUS, HITS_BONUS, OBJECT_LYING, VILLAIN_WANDER and FIND_WANDER.

Never while he is appearing (ARRIVING short of $70), nor unless his legs are standing or walking (graphics 16-47): not while he vanishes. TOUCH_TEST, the rest, is the overlap test every touching test in the game ends with, IX against IY: along U the distance between them, the whole 16-bit positions, must be less than IX's half-size plus half of IY's; the same along V; carry if both. The positions carry the cell, so things in neighbouring cells meet across the line between them.