Routines
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B0E7: Set a creature's step from the way it faces
Used by the routines at WANDERER and PACER.
Makes an index of bit 6 of the flags (the mirror bit) and bit 0 of the graphic, and copies the step in U and V from FACING_STEPS: one unit in the direction it faces. The callers double it.
Input
IX the creature
STEP_FROM_FACING B0E7 LD A,(IX+$07) bit 6 of the flags, turned into bit 1
B0EA RLCA
B0EB RLCA
B0EC RLCA
B0ED AND $02
B0EF LD B,A
B0F0 LD A,(IX+$00) with bit 0 of the graphic: 0 to 3, doubled
B0F3 AND $01
B0F5 OR B
B0F6 SLA A
B0F8 LD HL,FACING_STEPS its pair in the table
B0FB CALL ADD_HL_A
B0FE LD A,(HL) its steps in U and V
B0FF INC HL
B100 LD (IX+$09),A
B103 LD A,(HL)
B104 LD (IX+$0A),A
B107 RET
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