The rest of the author's ANIM (KNIGHT_CONTROLS), and then the common end of every object's update: INPE sets the sprite, KON6 takes the direction, NOPROP adds gravity, NOG makes the direction into the three axes of the step, and the step is tried against every other record (FIND_OBSTACLE). If something is in the way, BUMPED deals with it: a door may take the knight to another room, anything else is met (OBJECTS_MEET) and the step tried again axis by axis (MEET_DECOY), which comes back to TRY_STEP here. When the step is clear the record gets the new state and place (ISO_MOVE), and the object is redrawn (REDRAW_OBJECT).

Gravity: unless the direction has bit 1 (rising), the up bit is cleared (by the constant $EF in IY+$0B) and down added (from the constant in IY+$05), so everything falls two units a pass until it is stopped. A fall sets bit 7 of the state, in the air, and while that is set CHE3D does not run the object's own case but keeps it going the way +18 says. A fall keeps only the down bit (and the low two), so everything falls straight down, the knight at the end of a jump too (measured). The air ends when the fall is stopped, or when the count in +15 runs out (it is 1 while falling, 3 for a bounce), and if it was in the air at the start of the pass and did not move at all, the object is updated again at once (CHE3D) as a thing on the ground. Bit 6 of IY+$7B, which MEET_DECOY sets when the step was stopped by an object of kind 2 or 3, makes it bounce: three passes going up.

The knight's screen position is worked out afresh on each pass: his record is first put back to one fixed point on the floor (50, 78, 50) and its place on the screen, and ISO_MOVE moves him from there. Everything else is moved from where it was.

On the first pass in a room (bit 2 of IY+$17, which the room's entry sets and MAIN_LOOP clears) nothing moves: the direction is cleared, but all three axis bits are set, so the test runs on a box one unit up x, two down and one down y from where the object is, and whatever that meets is dealt with as usual (BUMPED); then the record is only drawn. What the offset box is for is not worked out.