;;; $88B6: Move enemy projectile horizontally ;;;
{
;; Parameters:
;;     X: Enemy projectile index
;; Returns:
;;     Carry: Set if collided with block

; This routine expects:
;     Enemy projectile $1A27: X subposition
;     Enemy projectile $1AB7: X velocity (unit 1/100h px/frame)
$86:88B6 DA          PHX
$86:88B7 64 12       STZ $12    [$7E:0012]  ;\
$86:88B9 64 14       STZ $14    [$7E:0014]  ;|
$86:88BB BD B7 1A    LDA $1AB7,x[$7E:1AD9]  ;|
$86:88BE 10 02       BPL $02    [$88C2]     ;} $14.$12 = [enemy projectile X velocity] / 100h
$86:88C0 C6 14       DEC $14    [$7E:0014]  ;|
                                            ;|
$86:88C2 85 13       STA $13    [$7E:0013]  ;/
$86:88C4 BD B4 1B    LDA $1BB4,x[$7E:1BD6]  ;\
$86:88C7 29 FF 00    AND #$00FF             ;} $1E = [enemy projectile Y radius]
$86:88CA 85 1E       STA $1E    [$7E:001E]  ;/
$86:88CC BD B3 1B    LDA $1BB3,x[$7E:1BD5]  ;\
$86:88CF 29 FF 00    AND #$00FF             ;} $1C = [enemy projectile X radius]
$86:88D2 85 1C       STA $1C    [$7E:001C]  ;/
$86:88D4 BD 93 1A    LDA $1A93,x[$7E:1AB5]  ;\
$86:88D7 38          SEC                    ;|
$86:88D8 E5 1E       SBC $1E    [$7E:001E]  ;|
$86:88DA 29 F0 FF    AND #$FFF0             ;|
$86:88DD 85 1A       STA $1A    [$7E:001A]  ;|
$86:88DF BD 93 1A    LDA $1A93,x[$7E:1AB5]  ;|
$86:88E2 18          CLC                    ;|
$86:88E3 65 1E       ADC $1E    [$7E:001E]  ;|
$86:88E5 3A          DEC A                  ;} $1A = (enemy projectile bottom boundary) / 10h - (enemy projectile top boundary) / 10h (number of blocks left to check)
$86:88E6 38          SEC                    ;|
$86:88E7 E5 1A       SBC $1A    [$7E:001A]  ;|
$86:88E9 4A          LSR A                  ;|
$86:88EA 4A          LSR A                  ;|
$86:88EB 4A          LSR A                  ;|
$86:88EC 4A          LSR A                  ;|
$86:88ED 85 1A       STA $1A    [$7E:001A]  ;/
$86:88EF 85 20       STA $20    [$7E:0020]  ; $20 = [$1A] (enemy projectile Y block span)
$86:88F1 BD 93 1A    LDA $1A93,x[$7E:1AB5]  ;\
$86:88F4 38          SEC                    ;|
$86:88F5 E5 1E       SBC $1E    [$7E:001E]  ;|
$86:88F7 4A          LSR A                  ;|
$86:88F8 4A          LSR A                  ;|
$86:88F9 4A          LSR A                  ;|
$86:88FA 4A          LSR A                  ;} Calculate (enemy projectile top boundary) / 10h * [room width in blocks] (target row block index)
$86:88FB E2 20       SEP #$20               ;|
$86:88FD 8D 02 42    STA $4202              ;|
$86:8900 AD A5 07    LDA $07A5  [$7E:07A5]  ;|
$86:8903 8D 03 42    STA $4203              ;|
$86:8906 C2 20       REP #$20               ;/
$86:8908 BD 27 1A    LDA $1A27,x[$7E:1A49]  ;\
$86:890B 18          CLC                    ;|
$86:890C 65 12       ADC $12    [$7E:0012]  ;|
$86:890E 85 16       STA $16    [$7E:0016]  ;} $18.$16 = [enemy projectile X position] + [$14].[$12]
$86:8910 BD 4B 1A    LDA $1A4B,x[$7E:1A6D]  ;|
$86:8913 65 14       ADC $14    [$7E:0014]  ;|
$86:8915 85 18       STA $18    [$7E:0018]  ;/
$86:8917 24 14       BIT $14    [$7E:0014]  ;\
$86:8919 30 06       BMI $06    [$8921]     ;} If [$14] >= 0:
$86:891B 18          CLC                    ;\
$86:891C 65 1C       ADC $1C    [$7E:001C]  ;} $22 = [$18] + [enemy projectile X radius] - 1 (target front boundary)
$86:891E 3A          DEC A                  ;/
$86:891F 80 03       BRA $03    [$8924]
$86:8921 38          SEC                    ;\ Else ([$14] < 0):
$86:8922 E5 1C       SBC $1C    [$7E:001C]  ;} $22 = [$18] - [enemy projectile X radius] (target front boundary)
$86:8924 85 22       STA $22    [$7E:0022]
$86:8926 4A          LSR A                  ;\
$86:8927 4A          LSR A                  ;|
$86:8928 4A          LSR A                  ;|
$86:8929 4A          LSR A                  ;|
$86:892A 18          CLC                    ;} X = ((target row block index) + (target front boundary) / 10h) * 2 (index of top block to check)
$86:892B 6D 16 42    ADC $4216              ;|
$86:892E 0A          ASL A                  ;|
$86:892F AA          TAX                    ;/
; LOOP
$86:8930 20 86 88    JSR $8886  [$86:8886]  ; Enemy projectile horizontal block reaction
$86:8933 B0 1A       BCS $1A    [$894F]     ; If solid: go to BRANCH_SOLID
$86:8935 8A          TXA                    ;\
$86:8936 18          CLC                    ;|
$86:8937 6D A5 07    ADC $07A5  [$7E:07A5]  ;} X += [room width in blocks] * 2 (next row)
$86:893A 6D A5 07    ADC $07A5  [$7E:07A5]  ;|
$86:893D AA          TAX                    ;/
$86:893E C6 1A       DEC $1A    [$7E:001A]  ; Decrement $1A
$86:8940 10 EE       BPL $EE    [$8930]     ; If [$1A] >= 0: go to LOOP
$86:8942 FA          PLX
$86:8943 A5 16       LDA $16    [$7E:0016]  ;\
$86:8945 9D 27 1A    STA $1A27,x[$7E:1A49]  ;|
$86:8948 A5 18       LDA $18    [$7E:0018]  ;} Enemy projectile X position = [$18].[$16]
$86:894A 9D 4B 1A    STA $1A4B,x[$7E:1A6D]  ;/
$86:894D 18          CLC                    ;\
$86:894E 60          RTS                    ;} Return carry clear
; BRANCH_SOLID
$86:894F FA          PLX
$86:8950 9E 27 1A    STZ $1A27,x[$7E:1A41]  ; Enemy projectile X subposition = 0
$86:8953 A5 22       LDA $22    [$7E:0022]
$86:8955 24 14       BIT $14    [$7E:0014]  ;\
$86:8957 30 10       BMI $10    [$8969]     ;} If [$14] < 0: go to BRANCH_MOVING_LEFT
$86:8959 29 F0 FF    AND #$FFF0             ;\
$86:895C 38          SEC                    ;|
$86:895D E5 1C       SBC $1C    [$7E:001C]  ;|
$86:895F DD 4B 1A    CMP $1A4B,x[$7E:1A5D]  ;} Enemy projectile X position = max([enemy projectile X position], (target front boundary) / 10h * 10h - [enemy projectile X radius])
$86:8962 90 03       BCC $03    [$8967]     ;|
$86:8964 9D 4B 1A    STA $1A4B,x[$7E:1A5D]  ;/
$86:8967 38          SEC                    ;\
$86:8968 60          RTS                    ;} Return carry set
; BRANCH_MOVING_LEFT
$86:8969 09 0F 00    ORA #$000F             ;\
$86:896C 38          SEC                    ;|
$86:896D 65 1C       ADC $1C    [$7E:001C]  ;|
$86:896F DD 4B 1A    CMP $1A4B,x[$7E:1A65]  ;|
$86:8972 F0 02       BEQ $02    [$8976]     ;} Enemy projectile X position = min([enemy projectile X position], (target front boundary) / 10h * 10h + 10h + [enemy projectile X radius])
$86:8974 B0 03       BCS $03    [$8979]     ;|
                                            ;|
$86:8976 9D 4B 1A    STA $1A4B,x[$7E:1A65]  ;/
$86:8979 38          SEC                    ;\
$86:897A 60          RTS                    ;} Return carry set
}