Routines
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ADA0: Draws all hazards
This includes all cars, barriers, tumbleweeds, etc.
Input
Used by the routines at main_loop, cpu_driver and escape_scene.
draw_hazards ADA0 XOR A var_a222 = 0
ADA1 LD ($A222),A
ADA4 LD IYh,$E3 IY = $E3xx
ADA7 LD IX,$A188 IX = &hazards[0]
ADAB LD DE,$0014 Stride of hazards entry in bytes
ADAE LD B,$06 6 iterations
dh_loop ADB0 RLC (IX+$00) Set carry if the hazard is active
ADB4 EXX Bank
ADB5 CALL C,dh_draw_one_hazard Call dh_draw_one_hazard if hazard active
ADB8 EXX Unbank
ADB9 ADD IX,DE Advance to next hazard
ADBB DJNZ dh_loop Loop while iterations remain -- B > 0
ADBD RET Return
dh_draw_one_hazard ADBE LD C,(IX+$0E) C = IX[14] -- top byte of horz position?
ADC1 LD A,(IX+$04) IX[4] -= IX[13] -- (TBD -= (bottom byte of horz position?))
ADC4 SUB (IX+$0D)
ADC7 LD (IX+$04),A
ADCA JR NC,draw_hazards_0 If IX[4] was < IX[13] Then C++
ADCC INC C
draw_hazards_0 ADCD LD A,(IX+$01) C += IX[1] -- distance related?
ADD0 ADD A,C
ADD1 LD C,A
ADD2 LD A,(IX+$0F) A = IX[15] + 1 -- counter?
ADD5 INC A
ADD6 JR NZ,dh_adf0 Jump to dh_adf0 if non-zero
ADD8 LD A,(IX+$11) A = IX[17] -- byte that indexes table_acdb
ADDB JR NC,draw_hazards_2 Jump if no carry (from earlier)
ADDD INC A Jump if ++A < 4
ADDE CP $04
ADE0 JR C,draw_hazards_1
ADE2 DEC A A--
ADE3 LD C,$FF C = $FF -- gets put in distance related field
draw_hazards_1 ADE5 LD (IX+$11),A IX[17] = A
draw_hazards_2 ADE8 AND A Set flags
ADE9 LD A,C A = C
ADEA JR Z,draw_hazards_3 Jump if zero
ADEC LD (IX+$01),A IX[1] = A -- update distance?
ADEF RET Return
dh_adf0 ADF0 LD A,C A = C
ADF1 CP $17 Jump if A < 23 -- still visible?
ADF3 JR C,draw_hazards_3
Wipe the hazard because it's gone?
ADF5 LD (IX+$00),$00 IX[0] = 0 -- hazard slot now spare
just_ret ADF9 RET Return
draw_hazards_3 ADFA LD (IX+$01),A IX[1] = A -- distance related
ADFD CP $14 Return if A >= 20
ADFF RET NC
AE00 DEC A A--
AE01 JR NZ,draw_hazards_6 Jump if non-zero
AE03 LD A,($A23F) A = ~(fast_counter & $E0)
AE06 AND $E0
AE08 CPL
AE09 CP (IX+$04) Jump if A >= IX[4]
AE0C JR NC,draw_hazards_5
AE0E LD B,(IX+$0F) B = IX[15] + 1
AE11 INC B
AE12 JR Z,draw_hazards_4 Jump if zero
Wipe the hazard because car overtaken?
AE14 LD (IX+$00),$00 IX[0] = 0 -- hazard slot now spare
AE18 RL B
AE1A RET NC Return if no carry
AE1B LD HL,$A22B Increment allow_overtake_bonus
AE1E INC (HL)
AE1F RET Return
draw_hazards_4 AE20 LD (IX+$04),A IX[4] = A
draw_hazards_5 AE23 XOR A A = 0
draw_hazards_6 AE24 ADD A,$4E A += $4E
$E300..$E316 is regularly accessed. $E300 is always $60, $E316 is always $A0
AE26 LD IYl,A IY.low = A -- i.e. $E300 | A
AE28 LD A,(IY+$01) A = IY[1]
AE2B LD C,A C = A
AE2C SUB (IY+$00) A -= IY[0] -- A is now the delta between adjacent elements
Multiplier. DE = multiplier. A = multiplicand. HL = result.
AE2F LD D,$00 DE = A; HL = 0
AE31 LD H,D
AE32 LD L,D
AE33 LD E,A
AE34 LD A,(IX+$04) A = IX[4]
AE37 LD B,$08 B = 8 -- iterations of multiply loop
draw_hazards_7 AE39 RLA Test top bit
AE3A JR NC,draw_hazards_8 If it carried out then add
AE3C ADD HL,DE
draw_hazards_8 AE3D ADD HL,HL Double
AE3E DJNZ draw_hazards_7 Loop
AE40 LD A,H A = H -- high part of result
AE41 RRA
AE42 LD (IX+$06),A IX[6] = A
AE45 NEG A = ~((C - A) << 1)
AE47 ADD A,C
AE48 ADD A,A
AE49 CPL
AE4A LD L,A HL = $E800 + A
AE4B LD H,$E8
AE4D LD D,(HL) D = *HL
AE4E DEC L HL--
AE4F LD E,(HL) E = *HL
AE50 LD H,$EC H = $EC
AE52 LD A,(HL) A = *HL
AE53 INC L L++
AE54 LD H,(HL) H = *HL
AE55 LD L,A L = A
AE56 AND A Set flags
AE57 LD ($AE71),DE Self modify 'LD HL,xxxx' @ AE70
AE5B SBC HL,DE HL -= DE
AE5D EX DE,HL Swap
AE5E LD HL,$0000 HL = 0
AE61 LD A,(IX+$05) A = IX[5]
Another multiplier.
AE64 LD B,$08 B = 8
draw_hazards_9 AE66 RLA A <<= 1
AE67 JR NC,draw_hazards_10 If it carried out then add
AE69 ADD HL,DE
draw_hazards_10 AE6A ADD HL,HL Double
AE6B DJNZ draw_hazards_9 Loop
AE6D LD A,H A = H
AE6E RRA
AE6F LD C,A C = A
AE70 LD HL,$0000 HL = <self modified> + BC
AE73 ADD HL,BC
AE74 LD (IX+$02),L wordat(IX + 2) = HL
AE77 LD (IX+$03),H
AE7A CALL sub_ad51 Call sub_ad51
AE7D LD D,(IX+$01) D = IX[1]
AE80 LD E,(IX+$04) E = IX[4]
AE83 LD HL,$A222 HL = &var_a222
AE86 LD A,(HL) A = *HL
AE87 INC (HL) (*HL)++
AE88 LD HL,$E900 HL -> table
AE8B AND A Set flags
AE8C JR Z,draw_hazards_13 Jump if zero
AE8E LD B,A Iterations
Loop starts
draw_hazards_11 AE8F LD A,D A = D
AE90 CP (HL) Compare to *HL
AE91 INC L L++
AE92 JR C,draw_hazards_12 Jump if A < *HL
AE94 JR NZ,draw_hazards_14 Jump if A != *HL
AE96 LD A,E A = E
AE97 CP (HL) Compare to *HL
AE98 JR C,draw_hazards_14 Jump if A < *HL
draw_hazards_12 AE9A INC L L += 3
AE9B INC L
AE9C INC L
AE9D DJNZ draw_hazards_11 Loop
draw_hazards_13 AE9F LD (HL),D wordat(HL) = DE; HL += 2
AEA0 INC L
AEA1 LD (HL),E
AEA2 INC L
AEA3 PUSH IX DE = IX
AEA5 POP DE
AEA6 LD (HL),E wordat(HL) = DE; HL++
AEA7 INC L
AEA8 LD (HL),D
AEA9 JR draw_hazards_15 Jump
draw_hazards_14 AEAB PUSH DE Preserve DE
AEAC LD A,B A = B * 4
AEAD ADD A,A
AEAE ADD A,A
AEAF LD C,A BC = A
AEB0 LD B,$00
AEB2 ADD A,$02 A += 2 + L
AEB4 ADD A,L
AEB5 LD E,A E = A
AEB6 SUB $04 A -= 4
AEB8 LD L,A L = A
AEB9 LD D,H D = H
AEBA LDDR Do *HL-- = *DE-- until BC == 0
AEBC EX DE,HL
AEBD PUSH IX DE = IX
AEBF POP DE
AEC0 LD (HL),D wordat(HL) = DE; HL -= 2
AEC1 DEC L
AEC2 LD (HL),E
AEC3 DEC L
AEC4 POP DE Restore DE
AEC5 LD (HL),E *HL = E
AEC6 DEC L L--
AEC7 LD (HL),D *HL = D
draw_hazards_15 AEC8 LD L,(IX+$0B) HL = wordat(IX + 11)
AECB LD H,(IX+$0C)
AECE JP (HL) Jump there
This entry point is used by the routine at main_loop_23.
draw_hazards_16 AECF LD HL,$0000 HL = <self modified>
AED2 LD A,B A = B
AED3 CP (HL) Return if A != *HL
AED4 RET NZ
AED5 DEC A A--
AED6 CP $0B Jump if A < 11
AED8 JR C,draw_hazards_17
AEDA LD A,$0A A = 10
draw_hazards_17 AEDC SRL A A >>= 1
AEDE LD ($AFFC),A Self modify 'LD A,x' @ AFFB
AEE1 LD E,A E = A
AEE2 RLCA A <<= 3
AEE3 RLCA
AEE4 RLCA
AEE5 SUB E A -= E
AEE6 LD E,A DE = A
AEE7 LD D,$00
draw_hazards_18 AEE9 INC L L += 2
AEEA INC L
AEEB LD A,(HL) IX = wordat(HL); HL += 2
AEEC LD IXl,A
AEEE INC L
AEEF LD A,(HL)
AEF0 LD IXh,A
AEF2 INC L
AEF3 PUSH HL Preserve HL, BC, DE
AEF4 PUSH BC
AEF5 PUSH DE
AEF6 LD H,(IX+$0A) HL = wordat(IX + 9)
AEF9 LD L,(IX+$09)
AEFC ADD HL,DE HL += DE
AEFD LD E,(HL) E = *HL
AEFE RLC E E <<= 3 ?
AF00 RLC E
AF02 RLC E
AF04 LD A,(IX+$06) A = IX[6] - IX[16]
AF07 SUB (IX+$10)
AF0A LD ($933E),A Self modify 'LD D,x' @ draw_object_right_8 to load A
AF0D LD A,(IX+$13) A = IX[19]
AF10 LD ($93C1),A Self modify 'LD A,x' @ 93C0 to load A
AF13 LD A,(IX+$0F) A = IX[15] + 1
AF16 INC A
AF17 JR Z,draw_hazards_23 Jump if zero
AF19 LD A,(IX+$03) A = IX[3]
AF1C AND A Set flags
AF1D LD A,(IX+$02) A = IX[2]
AF20 JP M,draw_hazards_19 Jump if negative
AF23 JP NZ,draw_hazards_22 Jump if non-zero
AF26 CP $80 Jump if A >= 128
AF28 JP NC,draw_hazards_21
AF2B ADD A,E A += E
AF2C JP draw_hazards_20 Jump
draw_hazards_19 AF2F ADD A,E A += E
AF30 JR NC,draw_hazards_22 Jump if no carry
draw_hazards_20 AF32 CALL draw_object_left_1
AF35 JP draw_hazards_22
draw_hazards_21 AF38 CALL draw_object_right_3
draw_hazards_22 AF3B POP DE
AF3C POP BC
AF3D XOR A Self modify 'LD A,x' @ 93C0 to load 0
AF3E LD ($93C1),A
AF41 LD HL,$A222 HL = &var_a222
AF44 DEC (HL) (*HL)--
AF45 POP HL Restore HL
AF46 RET Z Return if zero
AF47 LD A,(HL) A = *HL
AF48 CP B Jump if A == B
AF49 JP Z,draw_hazards_18
AF4C LD ($AED0),HL Self modify 'LD HL' @ draw_hazards_16 to load HL
AF4F RET Return
draw_hazards_23 AF50 LD A,(IX+$03) A = IX[3]
AF53 LD ($B02A),A Self modify 'LD A,x' @ B029 to load A
AF56 AND A Set flags
AF57 LD A,(IX+$02) A = IX[2]
AF5A LD ($B02D),A Self modify 'LD A,x' @ B02C to load A
AF5D JP M,draw_hazards_24 Jump if negative
AF60 JP NZ,draw_hazards_22 Jump if non-zero
AF63 CP $80 Jump if A >= 128
AF65 JP NC,draw_hazards_26
AF68 ADD A,E A = E
AF69 JP draw_hazards_25 Jump
draw_hazards_24 AF6C ADD A,E A = E
AF6D JR NC,draw_hazards_22 -- checking result of test at AF56?
draw_hazards_25 AF6F CALL draw_object_left_1
AF72 JP draw_hazards_27 Jump
draw_hazards_26 AF75 CALL draw_object_right_3
draw_hazards_27 AF78 LD A,($933E) Read A from 'LD D,x' @ draw_object_right_8
AF7B LD ($B024),A Self modify 'LD A,x' @ B023
AF7E LD A,($A232) Get smash_factor
AF81 CP $05 Jump if A >= 5
AF83 JR NC,draw_hazards_28
AF85 LD A,($AFFC) A = x in 'LD A,x' @ AFFB
AF88 CP $04 Jump if A >= 4
AF8A JP NC,draw_hazards_28
AF8D ADD A,A Double A
AF8E LD C,A BC = A
AF8F LD B,$00
AF91 LD HL,$CDEC HL = table_cdec + BC
AF94 ADD HL,BC
I see this getting hit only when in smash mode.
AF95 LD B,(HL) BC = wordat(HL)
AF96 INC HL
AF97 LD C,(HL)
AF98 LD HL,$E1D8
AF9B CALL draw_hazards_35
draw_hazards_28 AF9E LD A,($A232) Get smash_factor
AFA1 CP $04 Jump if it's < 4
AFA3 JR C,draw_hazards_29
AFA5 SUB $04 A = (A - 4) * 4 ?
AFA7 RLCA
AFA8 RLCA
AFA9 EX AF,AF' Bank
AFAA LD A,($AFFC) A = x in 'LD A,x' @ AFFB
AFAD RLCA *= 2
AFAE LD E,A DE = A
AFAF LD D,$00
AFB1 LD HL,$CE00 HL = table_ce00 + DE -- table?
AFB4 ADD HL,DE
AFB5 LD B,(HL) BC = wordat(HL); HL++
AFB6 INC HL
AFB7 LD C,(HL)
AFB8 EX AF,AF' Unbank
AFB9 LD E,A E = A
AFBA LD HL,$CDF4 another table?
AFBD LD A,($A236) Load counter_C AND 1
AFC0 AND $01
AFC2 RLCA A <<= 1?
AFC3 ADD A,E A += E
AFC4 LD E,A E = A
AFC5 ADD HL,DE HL += DE
AFC6 LD A,(HL) HL = wordat(HL)
AFC7 INC HL
AFC8 LD H,(HL)
AFC9 LD L,A
AFCA POP DE Retrieve DE from stack
AFCB PUSH DE
AFCC CALL draw_hazards_34
draw_hazards_29 AFCF LD A,($A232) Get smash_factor
AFD2 AND A Jump if zero
AFD3 JP Z,draw_hazards_22
AFD6 DEC A A--
AFD7 JR Z,draw_hazards_31 Jump if zero
AFD9 DEC A A--
AFDA JR Z,draw_hazards_30 Jump if zero
AFDC LD HL,$CE26 table?
AFDF CALL draw_hazards_32 Call aff1
draw_hazards_30 AFE2 LD HL,$CE0C
AFE5 CALL draw_hazards_32 Call aff1
draw_hazards_31 AFE8 LD HL,$CE19
AFEB CALL draw_hazards_32 Call aff1
AFEE JP draw_hazards_22
draw_hazards_32 AFF1 LD A,(HL) A = *HL - 1
AFF2 DEC A
AFF3 JP P,draw_hazards_33 Jump if +ve
AFF6 LD A,$05 A = 5 -- it became zero, reset to 5
draw_hazards_33 AFF8 LD (HL),A *HL = A
AFF9 LD E,A E = A
AFFA INC HL HL++
AFFB LD A,$00 A = <self modified>
AFFD LD C,A C = A
AFFE LD D,A D = A
AFFF ADD A,E A += E
B000 CP $06 Return if A >= 6
B002 RET NC
B003 LD E,A E = A
B004 SUB D A -= D
B005 LD D,A D = A
B006 SLA C C <<= 1
B008 LD B,$00 B = 0
B00A ADD HL,BC HL += BC
B00B LD A,(HL) A = *HL
B00C SUB D A -= D
B00D LD B,A B = A
B00E INC HL HL++
B00F LD C,(HL) C = *HL
E = smoke animation index Select the frame.
B010 LD A,E DE = E * 7
B011 ADD A,A
B012 ADD A,A
B013 ADD A,A
B014 SUB E
B015 LD E,A
B016 LD D,$00
B018 LD HL,$E1AE Point HL at smoke_defns
Similar code to $AA19.
draw_hazards_34 B01B ADD HL,DE HL += DE
draw_hazards_35 B01C LD E,(HL) E = *HL * 8 -- turn byte width to pixel width
B01D RLC E
B01F RLC E
B021 RLC E
B023 LD A,$00 A = <self modified> + B
B025 ADD A,B
B026 LD ($933E),A Self modify 'LD D,x' @ draw_object_right_8 to load A
B029 LD A,$00 A = <self modified>
B02B AND A Set flags
B02C LD A,$00 A = <self modified>
B02E JP M,draw_hazards_37 Jump to draw_hazards_37 if negative
B031 RET NZ Return if non-zero
B032 ADD A,C A += C
B033 RET C Return if carry
B034 CP $80 Jump to draw_object_right_3 if A >= 128
B036 JP NC,draw_object_right_3
draw_hazards_36 B039 ADD A,E A += E -- pixel width
B03A JP draw_object_left_1 Jump to draw_object_left_1
draw_hazards_37 B03D ADD A,C A += C
B03E JR C,draw_hazards_36 Loop? if carry
B040 ADD A,E A += E -- pixel width
B041 JP C,draw_object_left_1 Jump to draw_object_left_1 if carry
B044 RET Return
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