Used by the routine at MOVE_PLAYER.

First adds the nudge in +$0E and +$0F, which a doorway leaves to steer the robot onto its middle line (NUDGE_ALONG_V, NUDGE_ALONG_U), to the U and V steps, and clears it; then adds 3 in the direction he faces, through WALK_STEP_TBL. So the nudge acts only while he walks.

DISPATCH_ON_FACING, the last three instructions, jumps through a table of four addresses at BC by the facing of the object at IX (GET_SPRITE_DIR), using the main loop's jump through the update table (in AFTER_GAME). The exit check (HANDLE_EXIT_SCREEN) and a doorway's first pillar (FIRST_PILLAR) use it too.