Routines
Prev: 8A75 Up: Map Next: 8BBA
8ABB: Move Willy (1)
Used by the routine at 870E. This routine deals with Willy if he's jumping or falling.
8ABB LD A,($806B) Pick up the airborne status indicator from 806B
8ABE CP $01 Is Willy jumping?
8AC0 JR NZ,$8B10 Jump if not
Willy is currently jumping.
8AC2 LD A,($806E) Pick up the jumping animation counter (0-17) from 806E
8AC5 RES 0,A Now -8<=A<=8 (and A is even)
8AC7 SUB $08
8AC9 LD HL,$8068 Adjust Willy's y-coordinate at 8068 depending on where Willy is in the jump
8ACC ADD A,(HL)
8ACD LD (HL),A
8ACE CALL $8B82 Adjust Willy's attribute buffer location at 806C depending on his y-coordinate
8AD1 LD A,($803B) Pick up the attribute byte of the wall tile for the current cavern from 803B
8AD4 CP (HL) Is the top-left cell of Willy's sprite overlapping a wall tile?
8AD5 JP Z,$8BA2 Jump if so
8AD8 INC HL Point HL at the top-right cell occupied by Willy's sprite
8AD9 CP (HL) Is the top-right cell of Willy's sprite overlapping a wall tile?
8ADA JP Z,$8BA2 Jump if so
8ADD LD A,($806E) Increment the jumping animation counter at 806E
8AE0 INC A
8AE1 LD ($806E),A
8AE4 SUB $08 A=J-8, where J (1-18) is the new value of the jumping animation counter
8AE6 JP P,$8AEB Jump if J>=8
8AE9 NEG A=8-J (1<=J<=7, 1<=A<=7)
8AEB INC A A=1+ABS(J-8)
8AEC RLCA D=8*(1+ABS(J-8)); this value determines the pitch of the jumping sound effect (rising as Willy rises, falling as Willy falls)
8AED RLCA
8AEE RLCA
8AEF LD D,A
8AF0 LD C,$20 This value determines the duration of the jumping sound effect
8AF2 LD A,($8073) Pick up the border colour for the current cavern from 8073
8AF5 OUT ($FE),A Make a jumping sound effect
8AF7 XOR $18
8AF9 LD B,D
8AFA DJNZ $8AFA
8AFC DEC C
8AFD JR NZ,$8AF5
8AFF LD A,($806E) Pick up the jumping animation counter (1-18) from 806E
8B02 CP $12 Has Willy reached the end of the jump?
8B04 JP Z,$8B96 Jump if so
8B07 CP $10 Is the jumping animation counter now 16?
8B09 JR Z,$8B10 Jump if so
8B0B CP $0D Is the jumping animation counter now 13?
8B0D JP NZ,$8C83 Jump if not
If we get here, then Willy is standing on the floor, or he's falling, or his jumping animation counter is 13 (at which point Willy is on his way down and is exactly two cell-heights above where he started the jump) or 16 (at which point Willy is on his way down and is exactly one cell-height above where he started the jump).
8B10 LD A,($8068) Pick up Willy's y-coordinate from 8068
8B13 AND $0F Does Willy's sprite occupy six cells at the moment?
8B15 JR NZ,$8B51 Jump if so
8B17 LD HL,($806C) Pick up Willy's attribute buffer coordinates from 806C
8B1A LD DE,$0040 Point HL at the left-hand cell below Willy's sprite
8B1D ADD HL,DE
8B1E LD A,($8032) Pick up the attribute byte of the crumbling floor tile for the current cavern from 8032
8B21 CP (HL) Does the left-hand cell below Willy's sprite contain a crumbling floor tile?
8B22 CALL Z,$8BBA If so, make it crumble
8B25 LD A,($804D) Pick up the attribute byte of the first nasty tile for the current cavern from 804D
8B28 CP (HL) Does the left-hand cell below Willy's sprite contain a nasty tile?
8B29 JR Z,$8B51 Jump if so
8B2B LD A,($8056) Pick up the attribute byte of the second nasty tile for the current cavern from 8056
8B2E CP (HL) Does the left-hand cell below Willy's sprite contain a nasty tile?
8B2F JR Z,$8B51 Jump if so
8B31 INC HL Point HL at the right-hand cell below Willy's sprite
8B32 LD A,($8032) Pick up the attribute byte of the crumbling floor tile for the current cavern from 8032
8B35 CP (HL) Does the right-hand cell below Willy's sprite contain a crumbling floor tile?
8B36 CALL Z,$8BBA If so, make it crumble
8B39 LD A,($804D) Pick up the attribute byte of the first nasty tile for the current cavern from 804D
8B3C CP (HL) Does the right-hand cell below Willy's sprite contain a nasty tile?
8B3D JR Z,$8B51 Jump if so
8B3F LD A,($8056) Pick up the attribute byte of the second nasty tile for the current cavern from 8056
8B42 CP (HL) Does the right-hand cell below Willy's sprite contain a nasty tile?
8B43 JR Z,$8B51 Jump if so
8B45 LD A,($8020) Pick up the attribute byte of the background tile for the current cavern from 8020
8B48 CP (HL) Set the zero flag if the right-hand cell below Willy's sprite is empty
8B49 DEC HL Point HL at the left-hand cell below Willy's sprite
8B4A JP NZ,$8BDD Jump if the right-hand cell below Willy's sprite is not empty
8B4D CP (HL) Is the left-hand cell below Willy's sprite empty?
8B4E JP NZ,$8BDD Jump if not
8B51 LD A,($806B) Pick up the airborne status indicator from 806B
8B54 CP $01 Is Willy jumping?
8B56 JP Z,$8C83 Jump if so
If we get here, then Willy is either in the process of falling or just about to start falling.
8B59 LD HL,$806A Reset bit 1 at 806A: Willy is not moving left or right
8B5C RES 1,(HL)
8B5E OR A Is Willy already falling?
8B5F JP Z,$8B9C Jump if not
8B62 INC A Increment the airborne status indicator at 806B
8B63 LD ($806B),A
8B66 RLCA The value of D determines the pitch of the falling sound effect
8B67 RLCA
8B68 RLCA
8B69 RLCA
8B6A LD D,A
8B6B LD C,$20 This value determines the duration of the falling sound effect
8B6D LD A,($8073) Pick up the border colour for the current cavern from 8073
8B70 OUT ($FE),A Make a falling sound effect
8B72 XOR $18
8B74 LD B,D
8B75 DJNZ $8B75
8B77 DEC C
8B78 JR NZ,$8B70
8B7A LD A,($8068) Add 8 to Willy's y-coordinate at 8068; this moves Willy downwards by 4 pixels
8B7D ADD A,$08
8B7F LD ($8068),A
8B82 AND $F0 L=16*Y, where Y is Willy's screen y-coordinate (0-14)
8B84 LD L,A
8B85 XOR A Clear A and the carry flag
8B86 RL L Now L=32*(Y-8*INT(Y/8)), and the carry flag is set if Willy is in the lower half of the cavern (Y>=8)
8B88 ADC A,$5C H=0x5C or 0x5D (MSB of the address of Willy's location in the attribute buffer)
8B8A LD H,A
8B8B LD A,($806C) Pick up Willy's screen x-coordinate (1-29) from bits 0-4 at 806C
8B8E AND $1F
8B90 OR L Now L holds the LSB of Willy's attribute buffer address
8B91 LD L,A
8B92 LD ($806C),HL Store Willy's updated attribute buffer location at 806C
8B95 RET
Willy has just finished a jump.
8B96 LD A,$06 Set the airborne status indicator at 806B to 0x06: Willy will continue to fall unless he's landed on a wall or floor block
8B98 LD ($806B),A
8B9B RET
Willy has just started falling.
8B9C LD A,$02 Set the airborne status indicator at 806B to 0x02
8B9E LD ($806B),A
8BA1 RET
The top-left or top-right cell of Willy's sprite is overlapping a wall tile.
8BA2 LD A,($8068) Adjust Willy's y-coordinate at 8068 so that the top row of cells of his sprite is just below the wall tile
8BA5 ADD A,$10
8BA7 AND $F0
8BA9 LD ($8068),A
8BAC CALL $8B82 Adjust Willy's attribute buffer location at 806C to account for this new y-coordinate
8BAF LD A,$02 Set the airborne status indicator at 806B to 0x02: Willy has started falling
8BB1 LD ($806B),A
8BB4 LD HL,$806A Reset bit 1 at 806A: Willy is not moving left or right
8BB7 RES 1,(HL)
8BB9 RET
Prev: 8A75 Up: Map Next: 8BBA