Routines
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DD01: Move a record by its step
Used by the routines at CREATURE_UPDATE, MONSTER112_UPDATE, WANDERING_MONSTER, SPARKLE_FLY, ANTIBODY_FLIGHT, OBJECT_FLIGHT, VILLAIN_WANDER, FIND_WANDER and WALK_ON.
Adds the step, two signed bytes, to U and V. Called after the step has been trimmed at the walls (MOVE_CLIPPED).
Input
IX The record
APPLY_STEP DD01 LD A,(IX+$0A) U plus the U step, sign-extended
DD04 CALL SIGN_EXTEND_A
DD07 LD C,(IX+$01)
DD0A LD B,(IX+$02)
DD0D ADD HL,BC
DD0E LD (IX+$01),L
DD11 LD (IX+$02),H
DD14 LD A,(IX+$0B) V plus the V step
DD17 CALL SIGN_EXTEND_A
DD1A LD C,(IX+$03)
DD1D LD B,(IX+$04)
DD20 ADD HL,BC
DD21 LD (IX+$03),L
DD24 LD (IX+$04),H
DD27 RET
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