Routines
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90E0: Add score points for a hit target
Adds points to the current player's score. The value in A is BCD-encoded as score/10: high nibble increments the 10s digit (×100 displayed points), low nibble increments the 1s digit (×10 displayed points). The trailing zero in the score display provides the ×10 factor. E.g. POINTS_TANK = BCD 25 → 2×100 + 5×10 = 250 points.
Input
A Points to add in BCD/10 format (e.g. BCD 25 = 250 points).
add_points 90E0 PUSH AF Extract high nibble (hundreds digit), skip if zero.
90E1 SRL A
90E3 SRL A
90E5 SRL A
90E7 SRL A
90E9 CP $00
90EB JP Z,add_points_units_entry
add_points_tens_loop 90EE PUSH AF Increment 10s score digit once per high-nibble unit.
90EF LD A,$02
90F1 CALL update_score
90F4 POP AF
90F5 DEC A
90F6 JR NZ,add_points_tens_loop
add_points_units_entry 90F8 POP AF Extract low nibble (tens digit), return if zero.
90F9 AND $0F
90FB CP $00
90FD RET Z
add_points_units_loop 90FE PUSH AF Increment 1s score digit once per low-nibble unit.
90FF LD A,$01
9101 CALL update_score
9104 POP AF
9105 DEC A
9106 JR NZ,add_points_units_loop
9108 RET
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