Routines
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DC37: Reverse Direction
Used by the routines at Handler_MovingObjects and Handler_Enemies.
Negates both deltas and flips facing when the horizontal delta is non-zero.
Input
IX Entity record
Negate the vertical delta.
Reverse_Direction DC37 LD A,(IX+$09) Fetch the vertical delta and decrease it by one.
DC3A DEC A
DC3B XOR %11111111 Invert every bit.
DC3D LD (IX+$09),A Write the negated vertical delta.
Negate the horizontal delta.
DC40 LD A,(IX+$08) Fetch the horizontal delta and decrease it by one.
DC43 DEC A
DC44 XOR %11111111 Invert every bit.
DC46 LD (IX+$08),A Write the negated horizontal delta.
DC49 RET Z Return if it is now zero.
Flip the facing bit.
DC4A LD A,$80 Toggle bit 7 of *IX+07.
DC4C XOR (IX+$07)
DC4F LD (IX+$07),A
DC52 RET Return.
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