Krakout: Steer an object toward a target object

C91C: Steer an object toward a target object

Sets the heading of the object that steers, in its logic record, to one of eight headings. That heading points from its sprite position toward a target object's sprite position.

Input
IY	logic record of the object that steers (obj2_record); its heading receives the result
IX	sprite record of the object that steers (object_table), read for its position
B	target's pool-slot index: 0 for the bat, 1 for ball A

Both objects' positions are read from their sprite records. X increases rightward and Y increases downward. The heading is the direction of the vector from the steerer to the target. The headings run clockwise: 0 for up, 2 for right, 4 for down and 6 for left, with the diagonals between them. Equal X yields 0 (target level or above) or 4 (target below). Equal Y yields 2 (target right) or 6 (target left).

head_toward_target

C91C

PUSH IY

Save the steerer's records and the target id across the slot lookup.

C91E

PUSH BC

C91F

PUSH IX

C921

LD A,B

Point IY at target slot B's sprite record. IX stays on the steerer's own sprite record.

C922