Norman Sword
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Norman Sword got a reaction from UncleWan in MM and JSW ports to SDL2
from the post above
Are you planning on doing JSW2 at any point? (For one, I always preferred JSW2 and secondly (and more selfishly), I'd love to look at the difference between the movement code between the first and second games.)
The code for JSW2 was not a rewrite of Matthews code. It was writen from scratch, using just visual information from the original. e.g. Look at the game mechanics, and write the code. JSW's method of movement was not even looked at (source code or dissassembly)
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Norman Sword got a reaction from Spider in What does NCB mean?
It does indeed mean National Coal Board.
Software projects received a threatening letter from the National Coal Board, about usage of the NCB logo without permission. Remember this was at the same time as Mr Arthur Scargill, was having a good laugh with the NCB.
Whilst the games MM and JSW do not have reference to The NCB (directly), the artist( Roger Tissyman) responsible for the cover design of the software projects release of these two games inserted the NCB graphic into his artwork.
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Norman Sword got a reaction from JianYang in What does NCB mean?
It does indeed mean National Coal Board.
Software projects received a threatening letter from the National Coal Board, about usage of the NCB logo without permission. Remember this was at the same time as Mr Arthur Scargill, was having a good laugh with the NCB.
Whilst the games MM and JSW do not have reference to The NCB (directly), the artist( Roger Tissyman) responsible for the cover design of the software projects release of these two games inserted the NCB graphic into his artwork.
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Norman Sword got a reaction from UncleWan in What does NCB mean?
It does indeed mean National Coal Board.
Software projects received a threatening letter from the National Coal Board, about usage of the NCB logo without permission. Remember this was at the same time as Mr Arthur Scargill, was having a good laugh with the NCB.
Whilst the games MM and JSW do not have reference to The NCB (directly), the artist( Roger Tissyman) responsible for the cover design of the software projects release of these two games inserted the NCB graphic into his artwork.
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Norman Sword got a reaction from CPL in MM Movement and Collision Detection explanation
A big post of z80 code
The reason for the left right anomaly is simply caused by poor code layout as done by Matthew.
When setting up movement code - it is normal to mirror the code for left and right. This simple procedure allows quick and accurate visual comparisons.
Here the first lot of code is the layout of checking left and right movement when possibly on a ramp
NOTE this has unused opcodes and does not mirror left and right
Expect visual changes - over time on what you can see here. I will probably edit the visual layout.
And correct errors as I see them.
MATTHEWS CODE:-
Used by the routines at 8DD3 and 8ED4. This routine moves Willy left or right if necessary.
8FBC LD A,($85D0) Pick up Willy's direction and movement flags from 85D0
8FBF AND $02 Is Willy moving left or right?
8FC1 RET Z Return if not
8FC2 LD A,($85D6) Pick up the rope status indicator from 85D6
8FC5 DEC A Is Willy on a rope?
8FC6 BIT 7,A
8FC8 RET Z Return if so (Willy's movement along a rope is handled at 935E)
8FC9 LD A,($85D0) Pick up Willy's direction and movement flags from 85D0
8FCC AND $01 Is Willy facing right?
8FCE JP Z,$9042 Jump if so
; LEFT AND RIGHT CODE - DISPLAYED NEXT TO EACH OTHER
Willy is moving right. ; Willy is moving left.
9042 LD A,($85D2) ; 8FD1 LD A,($85D2) Willy's animation frame from 85D2
9045 CP $03 ; 8FD4 OR A Is it 0?
9047 JR Z,$904E ; 8FD5 JR Z,$8FDC If so, jump to move Willy's sprite left across a cell boundary
9049 INC A ; 8FD7 DEC A Change Willy's animation frame at 85D2
904A LD ($85D2),A ;8FD8 LD ($85D2),A
904D RET ; 8FDB RET
Willy's sprite is moving right ; Willy's sprite is moving left across a cell boundary.
In the comments that follow, (x,y) refers to the coordinates of the top-left
cell currently occupied by Willy's sprite.
904E LD A,($85D1) ; 8FDC LD A,($85D1) Pick up the airborne status indicator from 85D1
9051 LD BC,$0000 ; 8FDF LD BC,$0000 Prepare BC for later addition
9054 OR A ; 8FE2 CP $00 Is Willy jumping?
9055 JR NZ,$9078 ; 8FE4 JR NZ,$900A Jump if so
9057 LD HL,($85D3) ; 8FE6 LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
; 8FE9 LD BC,$0000 Prepare BC for later addition (again, redundantly)
905A LD A,($80DA) ; 8FEC LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
905D DEC A ; 8FEF DEC A Now A=0x1F if the ramp goes up to the left, or 0x41 if it goes up to the right
905E OR $9D ; 8FF0 OR $A1
9060 XOR $BF ; 8FF2 XOR $E0
9062 LD E,A ; 8FF4 LD E,A Point HL at the cell at (x-1,y+1) if the ramp goes up to the left, or at the cell at
(x+1,y+2) if the ramp goes up to the right
9063 LD D,$00 ; 8FF5 LD D,$00
9065 ADD HL,DE ; 8FF7 ADD HL,DE
9066 LD A,($80C4) ; 8FF8 LD A,($80C4) Pick up the attribute byte of the ramp tile for the current room from 80C4
9069 CP (HL) ; 8FFB CP (HL) Is there a ramp tile in the cell pointed to by HL?
906A JR NZ,$9078 ; 8FFC JR NZ,$900A Jump if not
906C LD BC,$0020 ; 8FFE LD BC,$0020 Prepare BC for later addition
906F LD A,($80DA) ; 9001 LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
9072 OR A ; 9004 OR A Does the ramp go up to the right?
9073 JR Z,$9078 ; 9005 JR NZ,$900A Jump if so
9075 LD BC,$FFE0 ; 9007 LD BC,$FFE0 BC=-32 (the ramp goes up to the left)
9078 LD HL,($85D3) ; 900A LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
; check extremes far right ; and far left - jump room
907B ADD HL,BC ;
907C INC HL ;
907D INC HL ;
907E LD A,L ; 900D LD A,L Is Willy's screen x-coordinate 0 (on the far left)?
907F AND $1F ; 900E AND $1F
9081 JP Z,$949E ; 9010 JP Z,$948A If so, move Willy into the room to the left;
9084 LD DE,$0020 ;
9087 LD A,($80B2) ;
; 9013 ADD HL,BC Point HL at the cell at (x-1,y+1), or at the cell at (x-1,y) if Willy is on or about to step
onto a ramp that goes up to the left, or at the cell at (x-1,y+2) if Willy is walking down a ramp
; 9014 DEC HL
; 9015 LD DE,$0020
908A ADD HL,DE ; 9018 ADD HL,DE
; 9019 LD A,($80B2) Pick up the attribute byte of the wall tile for the current room from 80B2
908B CP (HL) ; 901C CP (HL) Is there a wall tile in the cell pointed to by HL?
908C RET Z ; 901D RET Z Return if so without moving Willy (his path is blocked)
908D LD A,($85CF) ; 901E LD A,($85CF) Pick up Willy's y-coordinate (Y) from 85CF
9090 SRA C ; 9021 SRA C Now B=Y (if Willy is neither on nor about to step onto a ramp), or Y+16
(if Willy is walking down a ramp),
or Y-16 (if Willy is on or about to step onto a ramp that goes up to the left)
this will be Willy's new y-coordinate
9092 ADD A,C ; 9023 ADD A,C
9093 LD B,A ; 9024 LD B,A
9094 AND $0F ; 9025 AND $0F Is Willy at a point in a jump (left) where his sprite occupies three rows of cells?
9096 JR Z,$90A1 ; 9027 JR Z,$9032 Jump if not (Willy's sprite is cell-aligned)
9098 LD A,($80B2) ; 9029 LD A,($80B2) Pick up the attribute byte of the wall tile for the current room from 80B2
909B ADD HL,DE ; 902C ADD HL,DE Point HL at the cell at (x-1,y+2)
909C CP (HL) ; 902D CP (HL) Is there a wall tile there?
909D RET Z ; 902E RET Z Return if so without moving Willy (his path is blocked)
909E OR A ; 902F OR A Point HL at the cell at (x-1,y+1)
909F SBC HL,DE ; 9030 SBC HL,DE
90A1 LD A,($80B2) ;
90A4 OR A ; 9032 OR A Point HL at the cell at (x-1,y), or at the cell at (x-1,y-1) if Willy is on or about
to step onto a ramp that goes up to the left, or at the cell at (x-1,y+1) if Willy
is walking down a ramp
90A5 SBC HL,DE ; 9033 SBC HL,DE
90A7 CP (HL) ;
90A8 RET Z ;
90A9 DEC HL ;
90AA LD ($85D3),HL ; 9035 LD ($85D3),HL Save Willy's new attribute buffer coordinates (in HL) at 85D3
90AD XOR A
90AE LD ($85D2),A ;
90B1 LD A,B ; 9038 LD A,B Save Willy's new y-coordinate at 85CF ;
90B2 LD ($85CF),A ; 9039 LD ($85CF),A
90B5 RET ; 903C LD A,$03 Change Willy's animation frame at 85D2 from 0 to 3
; 903E LD ($85D2),A
; 9041 RET
;=============================================
The above code laid out with symatry - NOTE the bug can be inserted by just removing the head check.
Here I relay out the code with symetry
Used by the routines at 8DD3 and 8ED4. This routine moves Willy left or right if necessary.
8FC2:
LD A,($85D6) Pick up the rope status indicator from 85D6
DEC A Is Willy on a rope?
RET m Return if so (Willy's movement along a rope is handled at 935E)
LD A,($85D0) Pick up Willy's direction and movement flags from 85D0
bit 1,a Is Willy moving left or right?
RET Z Return if not
bit 0,a Is Willy facing right?
;set up some data for later
LD A,($85D2) Pick up Willy's animation frame from 85D2
LD BC,$0000 set no displacement in bc
JP Z,rampR Jump if facing right
Code would drop through to rampL
Willy is moving right. ; Willy is moving left.
rampR: ;rampL
CP $03 OR A Is it 0?
JR Z,right ; JR Z,left If so, jump to move Willy's sprite left across a cell boundary
INC A ; DEC A Decrement Willy's animation frame at 85D2
LD ($85D2),A ; LD ($85D2),A
RET ; RET
Willy's sprite is moving right ; Willy's sprite is moving left across a cell boundary.
In the comments that follow, (x,y) refers to the
coordinates of the top-left cell currently occupied by Willy's sprite.
right: ; left
LD A,($85D1) LD A,($85D1) Pick up the airborne status indicator from 85D1
OR A ; OR A Is Willy jumping?
JR NZ,nrampR ; JR NZ,nrampL Jump if so - NO RAMP ADJUSTMENT
LD HL,($85D3) ; LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
LD A,($80DA) ; LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
DEC A ; DEC A Now A=0x1F if the ramp goes up to the left, or 0x41 if it goes up to the right
OR $9D ; OR $A1
XOR $BF ; XOR $E0
LD E,A ; LD E,A Point HL at the cell at (x-1,y+1) if the ramp goes up to the left, or at the cell at (x+1,y+2)
if the ramp goes up to the right
LD D,$00 ; LD D,$00
ADD HL,DE ; ADD HL,DE
; is the ramp undefoot ?
LD A,($80C4) ; LD A,($80C4) Pick up the attribute byte of the ramp tile for the current room from 80C4
CP (HL) ; CP (HL) Is there a ramp tile in the cell pointed to by HL?
JR NZ,nrampR ; JR NZ,nrampL Jump if not
; set bc for ramp downwards
LD BC,$0020 ; LD BC,$0020 Prepare BC for later addition
LD A,($80DA) ; LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
OR A ; OR A Does the ramp go up to the right?
JR Z,nrampR ; JR NZ,nrampL Jump if so
; set bc for ramp upwards
LD BC,$FFE0 ; LD BC,$FFE0 BC=-32 (the ramp goes up to the left)
; before going any further check for going off screen
nrampR: ;nrampL:
LD HL,($85D3) ; LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
; position adjust
INC HL ;
INC HL ;
LD A,L ; LD A,L Is Willy's screen x-coordinate 0 (on the far left)?
AND $1F ; AND $1F
JP Z,$949E ; JP Z,$948A If so, move Willy into the room to the left;
; the above jumped room at the left/right edge
; adjust position if on a ramp - i.e move up/down - note bc=0 if not on a ramp
add hl,bc ; ADD HL,BC this is the ramp adjustment
; re align the checking for walls
; DEC HL
ld de,$0020 ; LD DE,$0020 Displacement for the tile below
ld a,($80b2) ; LD A,($80B2) Pick up the attribute byte of the wall tile for the current room from 80B2
LD B,A ; LD B,A save wall tile value in b
; head check - to implement bug - remove the check - can do either left or right - perhaps both
CP (HL) ; CP (HL) Is there a wall tile in the cell pointed to by HL?
RET Z ; RET Z Return if so without moving Willy (his path is blocked)
; BODY CHECK
ADD HL,DE ; ADD HL,DE
CP (HL) ; CP (HL)
RET Z ; RET Z
;calc new y position
LD A,($85CF) ; LD A,($85CF) Pick up Willy's y-coordinate (Y) from 85CF
SRA C ; SRA C Now B=Y (if Willy is neither on nor about to step onto a ramp), or Y+16
(if Willy is walking down a ramp), or Y-16 (if Willy is on or about to step onto a ramp
that goes up to the left); this will be Willy's new y-coordinate
ADD A,C ; ADD A,C
LD c,A ; LD c,A
; now check if cell aligned
AND $0F ; AND $0F Is Willy at a point in a jump (left) where his sprite occupies three rows of cells?
JR Z,ramp3R ; JR Z,ramp3L Jump if not (Willy's sprite is cell-aligned)
; if not aligned check 3rd tile
LD A,B ; LD A,B
ADD HL,DE ; ADD HL,DE Point HL at the cell at (x-1,y+2)
CP (HL) ; CP (HL) Is there a wall tile there?
RET Z ; RET Z Return if so without moving Willy (his path is blocked)
OR A ; OR A Point HL at the cell at (x-1,y+1)
SBC HL,DE ; SBC HL,DE restore back to position before 3rd tile was checked
; adjust position back to level with the top tile
ramp3R: ;ramp3L:
OR A ; OR A
SBC HL,DE ; SBC HL,DE
;
; and re REALIGN for top left
DEC HL ;
; save data and exit
LD ($85D3),HL ; LD ($85D3),HL Save Willy's new attribute buffer coordinates (in HL) at 85D3
ld a,c ; LD A,c Get Willy's new y-coordinate
LD ($85CF),A ; LD ($85CF),A Save Willy's new y-coordinate at 85CF
xor a ; LD A,$03 Change Willy's animation frame at 85D2 from 0 to 3
ld ($85d2),a ; LD ($85D2),A
RET ; RET
;==============================================
The Feature that is displayed in the movement code.
When it was implemented it allowed a feature and that feature was used.
It is similar to the pause bug, attic arrow bug, missing and uncollectable objects etc
Whilst I think my code is correct - if I notice errors - then I will correct them. The purpose of the code is to show code being laid out as similar for both directions.
;
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Norman Sword got a reaction from MtM in The Invisible Man
And to take all the work out of modification... The data needed is in my "INVISIBLE TAP" file
This is the minimum change needed to interact with willy - NOTE this omits the other changes I added
; to get this data look at these addresses in "INVISIBLE.TAP"-
; modification at start of rope draw - draw Willy to screen
at #92a4
call willy_draw_on (3 BYTES)
nop (1 BYTE)
old
LD IY,ytable (4 BYTES)
; with xor ??? if willy is present then no change here - leave to indicate looked at and aware of check
at #92c9
and (hl)
old (no change - read comment)
AND (HL)
; the rope pixel changes from {or} to {xor}
at #9311
xor (hl) (1 BYTE)
old
OR (HL) (1 BYTE)
; the final rope mode modification - get rid of Willy
at #935e
call willy_draw_off (3 BYTES)
old
LD A,(rope_status) (3 BYTES)
; Original Willy draw - now just saves data positions
at #9660
jp save_willy (3 BYTES)
old --- note 3 bytes which is the first instruction plus 1 byte from the next
LD B,#10 (2 BYTES)
LD A,(willy_att) (3 BYTES- ONLY FIRST BYTE NEEDS TO BE CHANGED)
; the code that is being called -
org #9f00
screen_pos dw 0
screen_def dw 0
save_willy:
ld a,(willy_att)
and #1f
or (ix+0) ; the x position
ld L,a
ld h,(ix+1)
ld (screen_pos),HL
ld (screen_def),de
ret
willy_pause:
ld hl,(screen_pos)
; shift from #60 to #40
res 5,h
call willy_xor1
LD DE,#0000
ret
willy_draw_on:
call willy_xor
LD IY,ytable
ret
willy_draw_off
call willy_xor
LD A,(rope_status)
ret
willy_xor:
ld hl,(screen_pos)
willy_xor1:
ld de,(screen_def)
draw_xor:
ld b,#10
loop_xor:
ld a,(de)
xor (hl)
ld (hl),a
inc de
inc L
ld a,(de)
xor (hl)
ld (hl),a
inc de
dec L
inc h
ld a,h
and 7
jr nz,legal_val
ld a,L
add a,#20
ld L,a
jr c,legal_val
ld a,h
sub 8
ld h,a
legal_val:
djnz loop_xor
ret
--------------------- PLUS
Stop dancing willy routine - delete call
remove Willy on plinth in death routine - delete call
-------------------------------
A lot of effort for something I am not doing ---
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Norman Sword got a reaction from JianYang in The Invisible Man
Just checked the code - was aware it seemed different from what I normally do - e.g. was part modifying someone elses code. I can see the layout does not adjust for the screen 1/3rds correctly. so here, is how I do it as opposed to modifying someone else's code --- Too much time doing this.
sprite_xor
ld b,#10
loop_xor:
ld a,(de)
xor (hl)
ld (hl),a
inc L
inc de
ld a,(de)
xor (hl)
ld (hl),a
dec L
inc de
inc h
ld a,h
and 7
jr nz,legal_val
ld a,L
add a,#20
ld L,a
jr c,legal_val
ld a,h
sub 8
ld h,a
legal_val:
djnz loop_xor
ret
Addendum:- just to show what I said works ---
1) no idea what version of jsw I have used - so no idea how many of the original bugs are present
2) deliberately not the same as the file you want to edit.
3) comes equiped with spray paint - Pause to show where willy is
4) due to the pause addition.... Can play by pressing pause to see where willy is and movement keys .eg hold "gh" and play as normal. Willy is treated as still invisible in the game code.
Addendum 2:- with a ghostbuster's radar - we track the invisible man.
And that concludes my effort.
INVISIBLE.tap
INVISIBLE_Tracking.tap
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Norman Sword got a reaction from Jet Set Willie in MM Movement and Collision Detection explanation
A big post of z80 code
The reason for the left right anomaly is simply caused by poor code layout as done by Matthew.
When setting up movement code - it is normal to mirror the code for left and right. This simple procedure allows quick and accurate visual comparisons.
Here the first lot of code is the layout of checking left and right movement when possibly on a ramp
NOTE this has unused opcodes and does not mirror left and right
Expect visual changes - over time on what you can see here. I will probably edit the visual layout.
And correct errors as I see them.
MATTHEWS CODE:-
Used by the routines at 8DD3 and 8ED4. This routine moves Willy left or right if necessary.
8FBC LD A,($85D0) Pick up Willy's direction and movement flags from 85D0
8FBF AND $02 Is Willy moving left or right?
8FC1 RET Z Return if not
8FC2 LD A,($85D6) Pick up the rope status indicator from 85D6
8FC5 DEC A Is Willy on a rope?
8FC6 BIT 7,A
8FC8 RET Z Return if so (Willy's movement along a rope is handled at 935E)
8FC9 LD A,($85D0) Pick up Willy's direction and movement flags from 85D0
8FCC AND $01 Is Willy facing right?
8FCE JP Z,$9042 Jump if so
; LEFT AND RIGHT CODE - DISPLAYED NEXT TO EACH OTHER
Willy is moving right. ; Willy is moving left.
9042 LD A,($85D2) ; 8FD1 LD A,($85D2) Willy's animation frame from 85D2
9045 CP $03 ; 8FD4 OR A Is it 0?
9047 JR Z,$904E ; 8FD5 JR Z,$8FDC If so, jump to move Willy's sprite left across a cell boundary
9049 INC A ; 8FD7 DEC A Change Willy's animation frame at 85D2
904A LD ($85D2),A ;8FD8 LD ($85D2),A
904D RET ; 8FDB RET
Willy's sprite is moving right ; Willy's sprite is moving left across a cell boundary.
In the comments that follow, (x,y) refers to the coordinates of the top-left
cell currently occupied by Willy's sprite.
904E LD A,($85D1) ; 8FDC LD A,($85D1) Pick up the airborne status indicator from 85D1
9051 LD BC,$0000 ; 8FDF LD BC,$0000 Prepare BC for later addition
9054 OR A ; 8FE2 CP $00 Is Willy jumping?
9055 JR NZ,$9078 ; 8FE4 JR NZ,$900A Jump if so
9057 LD HL,($85D3) ; 8FE6 LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
; 8FE9 LD BC,$0000 Prepare BC for later addition (again, redundantly)
905A LD A,($80DA) ; 8FEC LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
905D DEC A ; 8FEF DEC A Now A=0x1F if the ramp goes up to the left, or 0x41 if it goes up to the right
905E OR $9D ; 8FF0 OR $A1
9060 XOR $BF ; 8FF2 XOR $E0
9062 LD E,A ; 8FF4 LD E,A Point HL at the cell at (x-1,y+1) if the ramp goes up to the left, or at the cell at
(x+1,y+2) if the ramp goes up to the right
9063 LD D,$00 ; 8FF5 LD D,$00
9065 ADD HL,DE ; 8FF7 ADD HL,DE
9066 LD A,($80C4) ; 8FF8 LD A,($80C4) Pick up the attribute byte of the ramp tile for the current room from 80C4
9069 CP (HL) ; 8FFB CP (HL) Is there a ramp tile in the cell pointed to by HL?
906A JR NZ,$9078 ; 8FFC JR NZ,$900A Jump if not
906C LD BC,$0020 ; 8FFE LD BC,$0020 Prepare BC for later addition
906F LD A,($80DA) ; 9001 LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
9072 OR A ; 9004 OR A Does the ramp go up to the right?
9073 JR Z,$9078 ; 9005 JR NZ,$900A Jump if so
9075 LD BC,$FFE0 ; 9007 LD BC,$FFE0 BC=-32 (the ramp goes up to the left)
9078 LD HL,($85D3) ; 900A LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
; check extremes far right ; and far left - jump room
907B ADD HL,BC ;
907C INC HL ;
907D INC HL ;
907E LD A,L ; 900D LD A,L Is Willy's screen x-coordinate 0 (on the far left)?
907F AND $1F ; 900E AND $1F
9081 JP Z,$949E ; 9010 JP Z,$948A If so, move Willy into the room to the left;
9084 LD DE,$0020 ;
9087 LD A,($80B2) ;
; 9013 ADD HL,BC Point HL at the cell at (x-1,y+1), or at the cell at (x-1,y) if Willy is on or about to step
onto a ramp that goes up to the left, or at the cell at (x-1,y+2) if Willy is walking down a ramp
; 9014 DEC HL
; 9015 LD DE,$0020
908A ADD HL,DE ; 9018 ADD HL,DE
; 9019 LD A,($80B2) Pick up the attribute byte of the wall tile for the current room from 80B2
908B CP (HL) ; 901C CP (HL) Is there a wall tile in the cell pointed to by HL?
908C RET Z ; 901D RET Z Return if so without moving Willy (his path is blocked)
908D LD A,($85CF) ; 901E LD A,($85CF) Pick up Willy's y-coordinate (Y) from 85CF
9090 SRA C ; 9021 SRA C Now B=Y (if Willy is neither on nor about to step onto a ramp), or Y+16
(if Willy is walking down a ramp),
or Y-16 (if Willy is on or about to step onto a ramp that goes up to the left)
this will be Willy's new y-coordinate
9092 ADD A,C ; 9023 ADD A,C
9093 LD B,A ; 9024 LD B,A
9094 AND $0F ; 9025 AND $0F Is Willy at a point in a jump (left) where his sprite occupies three rows of cells?
9096 JR Z,$90A1 ; 9027 JR Z,$9032 Jump if not (Willy's sprite is cell-aligned)
9098 LD A,($80B2) ; 9029 LD A,($80B2) Pick up the attribute byte of the wall tile for the current room from 80B2
909B ADD HL,DE ; 902C ADD HL,DE Point HL at the cell at (x-1,y+2)
909C CP (HL) ; 902D CP (HL) Is there a wall tile there?
909D RET Z ; 902E RET Z Return if so without moving Willy (his path is blocked)
909E OR A ; 902F OR A Point HL at the cell at (x-1,y+1)
909F SBC HL,DE ; 9030 SBC HL,DE
90A1 LD A,($80B2) ;
90A4 OR A ; 9032 OR A Point HL at the cell at (x-1,y), or at the cell at (x-1,y-1) if Willy is on or about
to step onto a ramp that goes up to the left, or at the cell at (x-1,y+1) if Willy
is walking down a ramp
90A5 SBC HL,DE ; 9033 SBC HL,DE
90A7 CP (HL) ;
90A8 RET Z ;
90A9 DEC HL ;
90AA LD ($85D3),HL ; 9035 LD ($85D3),HL Save Willy's new attribute buffer coordinates (in HL) at 85D3
90AD XOR A
90AE LD ($85D2),A ;
90B1 LD A,B ; 9038 LD A,B Save Willy's new y-coordinate at 85CF ;
90B2 LD ($85CF),A ; 9039 LD ($85CF),A
90B5 RET ; 903C LD A,$03 Change Willy's animation frame at 85D2 from 0 to 3
; 903E LD ($85D2),A
; 9041 RET
;=============================================
The above code laid out with symatry - NOTE the bug can be inserted by just removing the head check.
Here I relay out the code with symetry
Used by the routines at 8DD3 and 8ED4. This routine moves Willy left or right if necessary.
8FC2:
LD A,($85D6) Pick up the rope status indicator from 85D6
DEC A Is Willy on a rope?
RET m Return if so (Willy's movement along a rope is handled at 935E)
LD A,($85D0) Pick up Willy's direction and movement flags from 85D0
bit 1,a Is Willy moving left or right?
RET Z Return if not
bit 0,a Is Willy facing right?
;set up some data for later
LD A,($85D2) Pick up Willy's animation frame from 85D2
LD BC,$0000 set no displacement in bc
JP Z,rampR Jump if facing right
Code would drop through to rampL
Willy is moving right. ; Willy is moving left.
rampR: ;rampL
CP $03 OR A Is it 0?
JR Z,right ; JR Z,left If so, jump to move Willy's sprite left across a cell boundary
INC A ; DEC A Decrement Willy's animation frame at 85D2
LD ($85D2),A ; LD ($85D2),A
RET ; RET
Willy's sprite is moving right ; Willy's sprite is moving left across a cell boundary.
In the comments that follow, (x,y) refers to the
coordinates of the top-left cell currently occupied by Willy's sprite.
right: ; left
LD A,($85D1) LD A,($85D1) Pick up the airborne status indicator from 85D1
OR A ; OR A Is Willy jumping?
JR NZ,nrampR ; JR NZ,nrampL Jump if so - NO RAMP ADJUSTMENT
LD HL,($85D3) ; LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
LD A,($80DA) ; LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
DEC A ; DEC A Now A=0x1F if the ramp goes up to the left, or 0x41 if it goes up to the right
OR $9D ; OR $A1
XOR $BF ; XOR $E0
LD E,A ; LD E,A Point HL at the cell at (x-1,y+1) if the ramp goes up to the left, or at the cell at (x+1,y+2)
if the ramp goes up to the right
LD D,$00 ; LD D,$00
ADD HL,DE ; ADD HL,DE
; is the ramp undefoot ?
LD A,($80C4) ; LD A,($80C4) Pick up the attribute byte of the ramp tile for the current room from 80C4
CP (HL) ; CP (HL) Is there a ramp tile in the cell pointed to by HL?
JR NZ,nrampR ; JR NZ,nrampL Jump if not
; set bc for ramp downwards
LD BC,$0020 ; LD BC,$0020 Prepare BC for later addition
LD A,($80DA) ; LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
OR A ; OR A Does the ramp go up to the right?
JR Z,nrampR ; JR NZ,nrampL Jump if so
; set bc for ramp upwards
LD BC,$FFE0 ; LD BC,$FFE0 BC=-32 (the ramp goes up to the left)
; before going any further check for going off screen
nrampR: ;nrampL:
LD HL,($85D3) ; LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
; position adjust
INC HL ;
INC HL ;
LD A,L ; LD A,L Is Willy's screen x-coordinate 0 (on the far left)?
AND $1F ; AND $1F
JP Z,$949E ; JP Z,$948A If so, move Willy into the room to the left;
; the above jumped room at the left/right edge
; adjust position if on a ramp - i.e move up/down - note bc=0 if not on a ramp
add hl,bc ; ADD HL,BC this is the ramp adjustment
; re align the checking for walls
; DEC HL
ld de,$0020 ; LD DE,$0020 Displacement for the tile below
ld a,($80b2) ; LD A,($80B2) Pick up the attribute byte of the wall tile for the current room from 80B2
LD B,A ; LD B,A save wall tile value in b
; head check - to implement bug - remove the check - can do either left or right - perhaps both
CP (HL) ; CP (HL) Is there a wall tile in the cell pointed to by HL?
RET Z ; RET Z Return if so without moving Willy (his path is blocked)
; BODY CHECK
ADD HL,DE ; ADD HL,DE
CP (HL) ; CP (HL)
RET Z ; RET Z
;calc new y position
LD A,($85CF) ; LD A,($85CF) Pick up Willy's y-coordinate (Y) from 85CF
SRA C ; SRA C Now B=Y (if Willy is neither on nor about to step onto a ramp), or Y+16
(if Willy is walking down a ramp), or Y-16 (if Willy is on or about to step onto a ramp
that goes up to the left); this will be Willy's new y-coordinate
ADD A,C ; ADD A,C
LD c,A ; LD c,A
; now check if cell aligned
AND $0F ; AND $0F Is Willy at a point in a jump (left) where his sprite occupies three rows of cells?
JR Z,ramp3R ; JR Z,ramp3L Jump if not (Willy's sprite is cell-aligned)
; if not aligned check 3rd tile
LD A,B ; LD A,B
ADD HL,DE ; ADD HL,DE Point HL at the cell at (x-1,y+2)
CP (HL) ; CP (HL) Is there a wall tile there?
RET Z ; RET Z Return if so without moving Willy (his path is blocked)
OR A ; OR A Point HL at the cell at (x-1,y+1)
SBC HL,DE ; SBC HL,DE restore back to position before 3rd tile was checked
; adjust position back to level with the top tile
ramp3R: ;ramp3L:
OR A ; OR A
SBC HL,DE ; SBC HL,DE
;
; and re REALIGN for top left
DEC HL ;
; save data and exit
LD ($85D3),HL ; LD ($85D3),HL Save Willy's new attribute buffer coordinates (in HL) at 85D3
ld a,c ; LD A,c Get Willy's new y-coordinate
LD ($85CF),A ; LD ($85CF),A Save Willy's new y-coordinate at 85CF
xor a ; LD A,$03 Change Willy's animation frame at 85D2 from 0 to 3
ld ($85d2),a ; LD ($85D2),A
RET ; RET
;==============================================
The Feature that is displayed in the movement code.
When it was implemented it allowed a feature and that feature was used.
It is similar to the pause bug, attic arrow bug, missing and uncollectable objects etc
Whilst I think my code is correct - if I notice errors - then I will correct them. The purpose of the code is to show code being laid out as similar for both directions.
;
-
Norman Sword got a reaction from Jet Set Willie in The Invisible Man
And to take all the work out of modification... The data needed is in my "INVISIBLE TAP" file
This is the minimum change needed to interact with willy - NOTE this omits the other changes I added
; to get this data look at these addresses in "INVISIBLE.TAP"-
; modification at start of rope draw - draw Willy to screen
at #92a4
call willy_draw_on (3 BYTES)
nop (1 BYTE)
old
LD IY,ytable (4 BYTES)
; with xor ??? if willy is present then no change here - leave to indicate looked at and aware of check
at #92c9
and (hl)
old (no change - read comment)
AND (HL)
; the rope pixel changes from {or} to {xor}
at #9311
xor (hl) (1 BYTE)
old
OR (HL) (1 BYTE)
; the final rope mode modification - get rid of Willy
at #935e
call willy_draw_off (3 BYTES)
old
LD A,(rope_status) (3 BYTES)
; Original Willy draw - now just saves data positions
at #9660
jp save_willy (3 BYTES)
old --- note 3 bytes which is the first instruction plus 1 byte from the next
LD B,#10 (2 BYTES)
LD A,(willy_att) (3 BYTES- ONLY FIRST BYTE NEEDS TO BE CHANGED)
; the code that is being called -
org #9f00
screen_pos dw 0
screen_def dw 0
save_willy:
ld a,(willy_att)
and #1f
or (ix+0) ; the x position
ld L,a
ld h,(ix+1)
ld (screen_pos),HL
ld (screen_def),de
ret
willy_pause:
ld hl,(screen_pos)
; shift from #60 to #40
res 5,h
call willy_xor1
LD DE,#0000
ret
willy_draw_on:
call willy_xor
LD IY,ytable
ret
willy_draw_off
call willy_xor
LD A,(rope_status)
ret
willy_xor:
ld hl,(screen_pos)
willy_xor1:
ld de,(screen_def)
draw_xor:
ld b,#10
loop_xor:
ld a,(de)
xor (hl)
ld (hl),a
inc de
inc L
ld a,(de)
xor (hl)
ld (hl),a
inc de
dec L
inc h
ld a,h
and 7
jr nz,legal_val
ld a,L
add a,#20
ld L,a
jr c,legal_val
ld a,h
sub 8
ld h,a
legal_val:
djnz loop_xor
ret
--------------------- PLUS
Stop dancing willy routine - delete call
remove Willy on plinth in death routine - delete call
-------------------------------
A lot of effort for something I am not doing ---
-
Norman Sword got a reaction from jetsetdanny in The Invisible Man
And to take all the work out of modification... The data needed is in my "INVISIBLE TAP" file
This is the minimum change needed to interact with willy - NOTE this omits the other changes I added
; to get this data look at these addresses in "INVISIBLE.TAP"-
; modification at start of rope draw - draw Willy to screen
at #92a4
call willy_draw_on (3 BYTES)
nop (1 BYTE)
old
LD IY,ytable (4 BYTES)
; with xor ??? if willy is present then no change here - leave to indicate looked at and aware of check
at #92c9
and (hl)
old (no change - read comment)
AND (HL)
; the rope pixel changes from {or} to {xor}
at #9311
xor (hl) (1 BYTE)
old
OR (HL) (1 BYTE)
; the final rope mode modification - get rid of Willy
at #935e
call willy_draw_off (3 BYTES)
old
LD A,(rope_status) (3 BYTES)
; Original Willy draw - now just saves data positions
at #9660
jp save_willy (3 BYTES)
old --- note 3 bytes which is the first instruction plus 1 byte from the next
LD B,#10 (2 BYTES)
LD A,(willy_att) (3 BYTES- ONLY FIRST BYTE NEEDS TO BE CHANGED)
; the code that is being called -
org #9f00
screen_pos dw 0
screen_def dw 0
save_willy:
ld a,(willy_att)
and #1f
or (ix+0) ; the x position
ld L,a
ld h,(ix+1)
ld (screen_pos),HL
ld (screen_def),de
ret
willy_pause:
ld hl,(screen_pos)
; shift from #60 to #40
res 5,h
call willy_xor1
LD DE,#0000
ret
willy_draw_on:
call willy_xor
LD IY,ytable
ret
willy_draw_off
call willy_xor
LD A,(rope_status)
ret
willy_xor:
ld hl,(screen_pos)
willy_xor1:
ld de,(screen_def)
draw_xor:
ld b,#10
loop_xor:
ld a,(de)
xor (hl)
ld (hl),a
inc de
inc L
ld a,(de)
xor (hl)
ld (hl),a
inc de
dec L
inc h
ld a,h
and 7
jr nz,legal_val
ld a,L
add a,#20
ld L,a
jr c,legal_val
ld a,h
sub 8
ld h,a
legal_val:
djnz loop_xor
ret
--------------------- PLUS
Stop dancing willy routine - delete call
remove Willy on plinth in death routine - delete call
-------------------------------
A lot of effort for something I am not doing ---
-
Norman Sword got a reaction from jetsetdanny in The Invisible Man
Just checked the code - was aware it seemed different from what I normally do - e.g. was part modifying someone elses code. I can see the layout does not adjust for the screen 1/3rds correctly. so here, is how I do it as opposed to modifying someone else's code --- Too much time doing this.
sprite_xor
ld b,#10
loop_xor:
ld a,(de)
xor (hl)
ld (hl),a
inc L
inc de
ld a,(de)
xor (hl)
ld (hl),a
dec L
inc de
inc h
ld a,h
and 7
jr nz,legal_val
ld a,L
add a,#20
ld L,a
jr c,legal_val
ld a,h
sub 8
ld h,a
legal_val:
djnz loop_xor
ret
Addendum:- just to show what I said works ---
1) no idea what version of jsw I have used - so no idea how many of the original bugs are present
2) deliberately not the same as the file you want to edit.
3) comes equiped with spray paint - Pause to show where willy is
4) due to the pause addition.... Can play by pressing pause to see where willy is and movement keys .eg hold "gh" and play as normal. Willy is treated as still invisible in the game code.
Addendum 2:- with a ghostbuster's radar - we track the invisible man.
And that concludes my effort.
INVISIBLE.tap
INVISIBLE_Tracking.tap
-
Norman Sword got a reaction from Jet Set Willie in The Invisible Man
Just checked the code - was aware it seemed different from what I normally do - e.g. was part modifying someone elses code. I can see the layout does not adjust for the screen 1/3rds correctly. so here, is how I do it as opposed to modifying someone else's code --- Too much time doing this.
sprite_xor
ld b,#10
loop_xor:
ld a,(de)
xor (hl)
ld (hl),a
inc L
inc de
ld a,(de)
xor (hl)
ld (hl),a
dec L
inc de
inc h
ld a,h
and 7
jr nz,legal_val
ld a,L
add a,#20
ld L,a
jr c,legal_val
ld a,h
sub 8
ld h,a
legal_val:
djnz loop_xor
ret
Addendum:- just to show what I said works ---
1) no idea what version of jsw I have used - so no idea how many of the original bugs are present
2) deliberately not the same as the file you want to edit.
3) comes equiped with spray paint - Pause to show where willy is
4) due to the pause addition.... Can play by pressing pause to see where willy is and movement keys .eg hold "gh" and play as normal. Willy is treated as still invisible in the game code.
Addendum 2:- with a ghostbuster's radar - we track the invisible man.
And that concludes my effort.
INVISIBLE.tap
INVISIBLE_Tracking.tap
-
Norman Sword got a reaction from Spider in The Invisible Man
Just checked the code - was aware it seemed different from what I normally do - e.g. was part modifying someone elses code. I can see the layout does not adjust for the screen 1/3rds correctly. so here, is how I do it as opposed to modifying someone else's code --- Too much time doing this.
sprite_xor
ld b,#10
loop_xor:
ld a,(de)
xor (hl)
ld (hl),a
inc L
inc de
ld a,(de)
xor (hl)
ld (hl),a
dec L
inc de
inc h
ld a,h
and 7
jr nz,legal_val
ld a,L
add a,#20
ld L,a
jr c,legal_val
ld a,h
sub 8
ld h,a
legal_val:
djnz loop_xor
ret
Addendum:- just to show what I said works ---
1) no idea what version of jsw I have used - so no idea how many of the original bugs are present
2) deliberately not the same as the file you want to edit.
3) comes equiped with spray paint - Pause to show where willy is
4) due to the pause addition.... Can play by pressing pause to see where willy is and movement keys .eg hold "gh" and play as normal. Willy is treated as still invisible in the game code.
Addendum 2:- with a ghostbuster's radar - we track the invisible man.
And that concludes my effort.
INVISIBLE.tap
INVISIBLE_Tracking.tap
-
Norman Sword got a reaction from Spider in The Invisible Man
because the sprite print routine adds pixels - it never erases pixels - similar to 1+4=5 or 1+3+2=6. The result never gets less no matter how many positive numbers you add.Although technically the print routine gives the result as (1 or 4 =5) and (1 or 3 or 2=3)
NOTE - the routine I mentioned uses XOR - and any number xor'd with itself is always 0. So how difficult is the xor version of the sprite print routine.
Original hacked to xor - call once to draw and once to erase.
sprite_xor
ld b,#10
loop_xor:
ld a,(de)
xor (hl)
ld (hl),a
inc L
inc de
ld a,(de)
xor (hl)
ld (hl),a
dec L
inc de
Inc h
ld a,h
and #07
jr nz,legal_val
ld a,h
sub 8
ld h,a
ld a,L
add a,#20
ld L,a
legal_val:
djnz loop_xor
ret
-
Norman Sword got a reaction from Spider in MM Movement and Collision Detection explanation
A big post of z80 code
The reason for the left right anomaly is simply caused by poor code layout as done by Matthew.
When setting up movement code - it is normal to mirror the code for left and right. This simple procedure allows quick and accurate visual comparisons.
Here the first lot of code is the layout of checking left and right movement when possibly on a ramp
NOTE this has unused opcodes and does not mirror left and right
Expect visual changes - over time on what you can see here. I will probably edit the visual layout.
And correct errors as I see them.
MATTHEWS CODE:-
Used by the routines at 8DD3 and 8ED4. This routine moves Willy left or right if necessary.
8FBC LD A,($85D0) Pick up Willy's direction and movement flags from 85D0
8FBF AND $02 Is Willy moving left or right?
8FC1 RET Z Return if not
8FC2 LD A,($85D6) Pick up the rope status indicator from 85D6
8FC5 DEC A Is Willy on a rope?
8FC6 BIT 7,A
8FC8 RET Z Return if so (Willy's movement along a rope is handled at 935E)
8FC9 LD A,($85D0) Pick up Willy's direction and movement flags from 85D0
8FCC AND $01 Is Willy facing right?
8FCE JP Z,$9042 Jump if so
; LEFT AND RIGHT CODE - DISPLAYED NEXT TO EACH OTHER
Willy is moving right. ; Willy is moving left.
9042 LD A,($85D2) ; 8FD1 LD A,($85D2) Willy's animation frame from 85D2
9045 CP $03 ; 8FD4 OR A Is it 0?
9047 JR Z,$904E ; 8FD5 JR Z,$8FDC If so, jump to move Willy's sprite left across a cell boundary
9049 INC A ; 8FD7 DEC A Change Willy's animation frame at 85D2
904A LD ($85D2),A ;8FD8 LD ($85D2),A
904D RET ; 8FDB RET
Willy's sprite is moving right ; Willy's sprite is moving left across a cell boundary.
In the comments that follow, (x,y) refers to the coordinates of the top-left
cell currently occupied by Willy's sprite.
904E LD A,($85D1) ; 8FDC LD A,($85D1) Pick up the airborne status indicator from 85D1
9051 LD BC,$0000 ; 8FDF LD BC,$0000 Prepare BC for later addition
9054 OR A ; 8FE2 CP $00 Is Willy jumping?
9055 JR NZ,$9078 ; 8FE4 JR NZ,$900A Jump if so
9057 LD HL,($85D3) ; 8FE6 LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
; 8FE9 LD BC,$0000 Prepare BC for later addition (again, redundantly)
905A LD A,($80DA) ; 8FEC LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
905D DEC A ; 8FEF DEC A Now A=0x1F if the ramp goes up to the left, or 0x41 if it goes up to the right
905E OR $9D ; 8FF0 OR $A1
9060 XOR $BF ; 8FF2 XOR $E0
9062 LD E,A ; 8FF4 LD E,A Point HL at the cell at (x-1,y+1) if the ramp goes up to the left, or at the cell at
(x+1,y+2) if the ramp goes up to the right
9063 LD D,$00 ; 8FF5 LD D,$00
9065 ADD HL,DE ; 8FF7 ADD HL,DE
9066 LD A,($80C4) ; 8FF8 LD A,($80C4) Pick up the attribute byte of the ramp tile for the current room from 80C4
9069 CP (HL) ; 8FFB CP (HL) Is there a ramp tile in the cell pointed to by HL?
906A JR NZ,$9078 ; 8FFC JR NZ,$900A Jump if not
906C LD BC,$0020 ; 8FFE LD BC,$0020 Prepare BC for later addition
906F LD A,($80DA) ; 9001 LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
9072 OR A ; 9004 OR A Does the ramp go up to the right?
9073 JR Z,$9078 ; 9005 JR NZ,$900A Jump if so
9075 LD BC,$FFE0 ; 9007 LD BC,$FFE0 BC=-32 (the ramp goes up to the left)
9078 LD HL,($85D3) ; 900A LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
; check extremes far right ; and far left - jump room
907B ADD HL,BC ;
907C INC HL ;
907D INC HL ;
907E LD A,L ; 900D LD A,L Is Willy's screen x-coordinate 0 (on the far left)?
907F AND $1F ; 900E AND $1F
9081 JP Z,$949E ; 9010 JP Z,$948A If so, move Willy into the room to the left;
9084 LD DE,$0020 ;
9087 LD A,($80B2) ;
; 9013 ADD HL,BC Point HL at the cell at (x-1,y+1), or at the cell at (x-1,y) if Willy is on or about to step
onto a ramp that goes up to the left, or at the cell at (x-1,y+2) if Willy is walking down a ramp
; 9014 DEC HL
; 9015 LD DE,$0020
908A ADD HL,DE ; 9018 ADD HL,DE
; 9019 LD A,($80B2) Pick up the attribute byte of the wall tile for the current room from 80B2
908B CP (HL) ; 901C CP (HL) Is there a wall tile in the cell pointed to by HL?
908C RET Z ; 901D RET Z Return if so without moving Willy (his path is blocked)
908D LD A,($85CF) ; 901E LD A,($85CF) Pick up Willy's y-coordinate (Y) from 85CF
9090 SRA C ; 9021 SRA C Now B=Y (if Willy is neither on nor about to step onto a ramp), or Y+16
(if Willy is walking down a ramp),
or Y-16 (if Willy is on or about to step onto a ramp that goes up to the left)
this will be Willy's new y-coordinate
9092 ADD A,C ; 9023 ADD A,C
9093 LD B,A ; 9024 LD B,A
9094 AND $0F ; 9025 AND $0F Is Willy at a point in a jump (left) where his sprite occupies three rows of cells?
9096 JR Z,$90A1 ; 9027 JR Z,$9032 Jump if not (Willy's sprite is cell-aligned)
9098 LD A,($80B2) ; 9029 LD A,($80B2) Pick up the attribute byte of the wall tile for the current room from 80B2
909B ADD HL,DE ; 902C ADD HL,DE Point HL at the cell at (x-1,y+2)
909C CP (HL) ; 902D CP (HL) Is there a wall tile there?
909D RET Z ; 902E RET Z Return if so without moving Willy (his path is blocked)
909E OR A ; 902F OR A Point HL at the cell at (x-1,y+1)
909F SBC HL,DE ; 9030 SBC HL,DE
90A1 LD A,($80B2) ;
90A4 OR A ; 9032 OR A Point HL at the cell at (x-1,y), or at the cell at (x-1,y-1) if Willy is on or about
to step onto a ramp that goes up to the left, or at the cell at (x-1,y+1) if Willy
is walking down a ramp
90A5 SBC HL,DE ; 9033 SBC HL,DE
90A7 CP (HL) ;
90A8 RET Z ;
90A9 DEC HL ;
90AA LD ($85D3),HL ; 9035 LD ($85D3),HL Save Willy's new attribute buffer coordinates (in HL) at 85D3
90AD XOR A
90AE LD ($85D2),A ;
90B1 LD A,B ; 9038 LD A,B Save Willy's new y-coordinate at 85CF ;
90B2 LD ($85CF),A ; 9039 LD ($85CF),A
90B5 RET ; 903C LD A,$03 Change Willy's animation frame at 85D2 from 0 to 3
; 903E LD ($85D2),A
; 9041 RET
;=============================================
The above code laid out with symatry - NOTE the bug can be inserted by just removing the head check.
Here I relay out the code with symetry
Used by the routines at 8DD3 and 8ED4. This routine moves Willy left or right if necessary.
8FC2:
LD A,($85D6) Pick up the rope status indicator from 85D6
DEC A Is Willy on a rope?
RET m Return if so (Willy's movement along a rope is handled at 935E)
LD A,($85D0) Pick up Willy's direction and movement flags from 85D0
bit 1,a Is Willy moving left or right?
RET Z Return if not
bit 0,a Is Willy facing right?
;set up some data for later
LD A,($85D2) Pick up Willy's animation frame from 85D2
LD BC,$0000 set no displacement in bc
JP Z,rampR Jump if facing right
Code would drop through to rampL
Willy is moving right. ; Willy is moving left.
rampR: ;rampL
CP $03 OR A Is it 0?
JR Z,right ; JR Z,left If so, jump to move Willy's sprite left across a cell boundary
INC A ; DEC A Decrement Willy's animation frame at 85D2
LD ($85D2),A ; LD ($85D2),A
RET ; RET
Willy's sprite is moving right ; Willy's sprite is moving left across a cell boundary.
In the comments that follow, (x,y) refers to the
coordinates of the top-left cell currently occupied by Willy's sprite.
right: ; left
LD A,($85D1) LD A,($85D1) Pick up the airborne status indicator from 85D1
OR A ; OR A Is Willy jumping?
JR NZ,nrampR ; JR NZ,nrampL Jump if so - NO RAMP ADJUSTMENT
LD HL,($85D3) ; LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
LD A,($80DA) ; LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
DEC A ; DEC A Now A=0x1F if the ramp goes up to the left, or 0x41 if it goes up to the right
OR $9D ; OR $A1
XOR $BF ; XOR $E0
LD E,A ; LD E,A Point HL at the cell at (x-1,y+1) if the ramp goes up to the left, or at the cell at (x+1,y+2)
if the ramp goes up to the right
LD D,$00 ; LD D,$00
ADD HL,DE ; ADD HL,DE
; is the ramp undefoot ?
LD A,($80C4) ; LD A,($80C4) Pick up the attribute byte of the ramp tile for the current room from 80C4
CP (HL) ; CP (HL) Is there a ramp tile in the cell pointed to by HL?
JR NZ,nrampR ; JR NZ,nrampL Jump if not
; set bc for ramp downwards
LD BC,$0020 ; LD BC,$0020 Prepare BC for later addition
LD A,($80DA) ; LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
OR A ; OR A Does the ramp go up to the right?
JR Z,nrampR ; JR NZ,nrampL Jump if so
; set bc for ramp upwards
LD BC,$FFE0 ; LD BC,$FFE0 BC=-32 (the ramp goes up to the left)
; before going any further check for going off screen
nrampR: ;nrampL:
LD HL,($85D3) ; LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
; position adjust
INC HL ;
INC HL ;
LD A,L ; LD A,L Is Willy's screen x-coordinate 0 (on the far left)?
AND $1F ; AND $1F
JP Z,$949E ; JP Z,$948A If so, move Willy into the room to the left;
; the above jumped room at the left/right edge
; adjust position if on a ramp - i.e move up/down - note bc=0 if not on a ramp
add hl,bc ; ADD HL,BC this is the ramp adjustment
; re align the checking for walls
; DEC HL
ld de,$0020 ; LD DE,$0020 Displacement for the tile below
ld a,($80b2) ; LD A,($80B2) Pick up the attribute byte of the wall tile for the current room from 80B2
LD B,A ; LD B,A save wall tile value in b
; head check - to implement bug - remove the check - can do either left or right - perhaps both
CP (HL) ; CP (HL) Is there a wall tile in the cell pointed to by HL?
RET Z ; RET Z Return if so without moving Willy (his path is blocked)
; BODY CHECK
ADD HL,DE ; ADD HL,DE
CP (HL) ; CP (HL)
RET Z ; RET Z
;calc new y position
LD A,($85CF) ; LD A,($85CF) Pick up Willy's y-coordinate (Y) from 85CF
SRA C ; SRA C Now B=Y (if Willy is neither on nor about to step onto a ramp), or Y+16
(if Willy is walking down a ramp), or Y-16 (if Willy is on or about to step onto a ramp
that goes up to the left); this will be Willy's new y-coordinate
ADD A,C ; ADD A,C
LD c,A ; LD c,A
; now check if cell aligned
AND $0F ; AND $0F Is Willy at a point in a jump (left) where his sprite occupies three rows of cells?
JR Z,ramp3R ; JR Z,ramp3L Jump if not (Willy's sprite is cell-aligned)
; if not aligned check 3rd tile
LD A,B ; LD A,B
ADD HL,DE ; ADD HL,DE Point HL at the cell at (x-1,y+2)
CP (HL) ; CP (HL) Is there a wall tile there?
RET Z ; RET Z Return if so without moving Willy (his path is blocked)
OR A ; OR A Point HL at the cell at (x-1,y+1)
SBC HL,DE ; SBC HL,DE restore back to position before 3rd tile was checked
; adjust position back to level with the top tile
ramp3R: ;ramp3L:
OR A ; OR A
SBC HL,DE ; SBC HL,DE
;
; and re REALIGN for top left
DEC HL ;
; save data and exit
LD ($85D3),HL ; LD ($85D3),HL Save Willy's new attribute buffer coordinates (in HL) at 85D3
ld a,c ; LD A,c Get Willy's new y-coordinate
LD ($85CF),A ; LD ($85CF),A Save Willy's new y-coordinate at 85CF
xor a ; LD A,$03 Change Willy's animation frame at 85D2 from 0 to 3
ld ($85d2),a ; LD ($85D2),A
RET ; RET
;==============================================
The Feature that is displayed in the movement code.
When it was implemented it allowed a feature and that feature was used.
It is similar to the pause bug, attic arrow bug, missing and uncollectable objects etc
Whilst I think my code is correct - if I notice errors - then I will correct them. The purpose of the code is to show code being laid out as similar for both directions.
;
-
Norman Sword got a reaction from Jet Set Willie in The Invisible Man
Because this would always be attributed to the original person. I have no incentive to add code to what (as far as I can see) is a simple deletion of the willy definition.
So in the words used on Dragons den "I'm out"
-------------------------------
path that could be taken - just not by me
1) To collide with the rope, Willy needs a definition. The deletion of Willies definition, means that path is out.
2) If the definition is intact
modify the code that draws willy - instead of actually putting the pixels to the screen- instead save the draw definition and the draw position, and return
in the rope draw routine - add a routine to use Willies draw definition and Willies draw position to xor Willy to the screen
Draw the rope - using xor - Willy will be flagged as collided in the normal way - movement on rope etc will still occur.
on rope exit add a routine to use Willies definition and Willies draw position to xor Willy off the screen.
The xor routine is a very simple sprite draw routine. Which would need adding,
The above allows Willy to interact with the rope....
The original modification was simply deleting Willies definition. This is adding ten times the effort of the original person to try and fix his hack.
Addendum:-
Just looked at this again - every reference to drawing willy elsewhere .. e.g the dancing Willies/ death screen etc. would need deleting.
-
Norman Sword got a reaction from jetsetdanny in The Invisible Man
because the sprite print routine adds pixels - it never erases pixels - similar to 1+4=5 or 1+3+2=6. The result never gets less no matter how many positive numbers you add.Although technically the print routine gives the result as (1 or 4 =5) and (1 or 3 or 2=3)
NOTE - the routine I mentioned uses XOR - and any number xor'd with itself is always 0. So how difficult is the xor version of the sprite print routine.
Original hacked to xor - call once to draw and once to erase.
sprite_xor
ld b,#10
loop_xor:
ld a,(de)
xor (hl)
ld (hl),a
inc L
inc de
ld a,(de)
xor (hl)
ld (hl),a
dec L
inc de
Inc h
ld a,h
and #07
jr nz,legal_val
ld a,h
sub 8
ld h,a
ld a,L
add a,#20
ld L,a
legal_val:
djnz loop_xor
ret
-
Norman Sword got a reaction from SymbolShift in MM Movement and Collision Detection explanation
A big post of z80 code
The reason for the left right anomaly is simply caused by poor code layout as done by Matthew.
When setting up movement code - it is normal to mirror the code for left and right. This simple procedure allows quick and accurate visual comparisons.
Here the first lot of code is the layout of checking left and right movement when possibly on a ramp
NOTE this has unused opcodes and does not mirror left and right
Expect visual changes - over time on what you can see here. I will probably edit the visual layout.
And correct errors as I see them.
MATTHEWS CODE:-
Used by the routines at 8DD3 and 8ED4. This routine moves Willy left or right if necessary.
8FBC LD A,($85D0) Pick up Willy's direction and movement flags from 85D0
8FBF AND $02 Is Willy moving left or right?
8FC1 RET Z Return if not
8FC2 LD A,($85D6) Pick up the rope status indicator from 85D6
8FC5 DEC A Is Willy on a rope?
8FC6 BIT 7,A
8FC8 RET Z Return if so (Willy's movement along a rope is handled at 935E)
8FC9 LD A,($85D0) Pick up Willy's direction and movement flags from 85D0
8FCC AND $01 Is Willy facing right?
8FCE JP Z,$9042 Jump if so
; LEFT AND RIGHT CODE - DISPLAYED NEXT TO EACH OTHER
Willy is moving right. ; Willy is moving left.
9042 LD A,($85D2) ; 8FD1 LD A,($85D2) Willy's animation frame from 85D2
9045 CP $03 ; 8FD4 OR A Is it 0?
9047 JR Z,$904E ; 8FD5 JR Z,$8FDC If so, jump to move Willy's sprite left across a cell boundary
9049 INC A ; 8FD7 DEC A Change Willy's animation frame at 85D2
904A LD ($85D2),A ;8FD8 LD ($85D2),A
904D RET ; 8FDB RET
Willy's sprite is moving right ; Willy's sprite is moving left across a cell boundary.
In the comments that follow, (x,y) refers to the coordinates of the top-left
cell currently occupied by Willy's sprite.
904E LD A,($85D1) ; 8FDC LD A,($85D1) Pick up the airborne status indicator from 85D1
9051 LD BC,$0000 ; 8FDF LD BC,$0000 Prepare BC for later addition
9054 OR A ; 8FE2 CP $00 Is Willy jumping?
9055 JR NZ,$9078 ; 8FE4 JR NZ,$900A Jump if so
9057 LD HL,($85D3) ; 8FE6 LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
; 8FE9 LD BC,$0000 Prepare BC for later addition (again, redundantly)
905A LD A,($80DA) ; 8FEC LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
905D DEC A ; 8FEF DEC A Now A=0x1F if the ramp goes up to the left, or 0x41 if it goes up to the right
905E OR $9D ; 8FF0 OR $A1
9060 XOR $BF ; 8FF2 XOR $E0
9062 LD E,A ; 8FF4 LD E,A Point HL at the cell at (x-1,y+1) if the ramp goes up to the left, or at the cell at
(x+1,y+2) if the ramp goes up to the right
9063 LD D,$00 ; 8FF5 LD D,$00
9065 ADD HL,DE ; 8FF7 ADD HL,DE
9066 LD A,($80C4) ; 8FF8 LD A,($80C4) Pick up the attribute byte of the ramp tile for the current room from 80C4
9069 CP (HL) ; 8FFB CP (HL) Is there a ramp tile in the cell pointed to by HL?
906A JR NZ,$9078 ; 8FFC JR NZ,$900A Jump if not
906C LD BC,$0020 ; 8FFE LD BC,$0020 Prepare BC for later addition
906F LD A,($80DA) ; 9001 LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
9072 OR A ; 9004 OR A Does the ramp go up to the right?
9073 JR Z,$9078 ; 9005 JR NZ,$900A Jump if so
9075 LD BC,$FFE0 ; 9007 LD BC,$FFE0 BC=-32 (the ramp goes up to the left)
9078 LD HL,($85D3) ; 900A LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
; check extremes far right ; and far left - jump room
907B ADD HL,BC ;
907C INC HL ;
907D INC HL ;
907E LD A,L ; 900D LD A,L Is Willy's screen x-coordinate 0 (on the far left)?
907F AND $1F ; 900E AND $1F
9081 JP Z,$949E ; 9010 JP Z,$948A If so, move Willy into the room to the left;
9084 LD DE,$0020 ;
9087 LD A,($80B2) ;
; 9013 ADD HL,BC Point HL at the cell at (x-1,y+1), or at the cell at (x-1,y) if Willy is on or about to step
onto a ramp that goes up to the left, or at the cell at (x-1,y+2) if Willy is walking down a ramp
; 9014 DEC HL
; 9015 LD DE,$0020
908A ADD HL,DE ; 9018 ADD HL,DE
; 9019 LD A,($80B2) Pick up the attribute byte of the wall tile for the current room from 80B2
908B CP (HL) ; 901C CP (HL) Is there a wall tile in the cell pointed to by HL?
908C RET Z ; 901D RET Z Return if so without moving Willy (his path is blocked)
908D LD A,($85CF) ; 901E LD A,($85CF) Pick up Willy's y-coordinate (Y) from 85CF
9090 SRA C ; 9021 SRA C Now B=Y (if Willy is neither on nor about to step onto a ramp), or Y+16
(if Willy is walking down a ramp),
or Y-16 (if Willy is on or about to step onto a ramp that goes up to the left)
this will be Willy's new y-coordinate
9092 ADD A,C ; 9023 ADD A,C
9093 LD B,A ; 9024 LD B,A
9094 AND $0F ; 9025 AND $0F Is Willy at a point in a jump (left) where his sprite occupies three rows of cells?
9096 JR Z,$90A1 ; 9027 JR Z,$9032 Jump if not (Willy's sprite is cell-aligned)
9098 LD A,($80B2) ; 9029 LD A,($80B2) Pick up the attribute byte of the wall tile for the current room from 80B2
909B ADD HL,DE ; 902C ADD HL,DE Point HL at the cell at (x-1,y+2)
909C CP (HL) ; 902D CP (HL) Is there a wall tile there?
909D RET Z ; 902E RET Z Return if so without moving Willy (his path is blocked)
909E OR A ; 902F OR A Point HL at the cell at (x-1,y+1)
909F SBC HL,DE ; 9030 SBC HL,DE
90A1 LD A,($80B2) ;
90A4 OR A ; 9032 OR A Point HL at the cell at (x-1,y), or at the cell at (x-1,y-1) if Willy is on or about
to step onto a ramp that goes up to the left, or at the cell at (x-1,y+1) if Willy
is walking down a ramp
90A5 SBC HL,DE ; 9033 SBC HL,DE
90A7 CP (HL) ;
90A8 RET Z ;
90A9 DEC HL ;
90AA LD ($85D3),HL ; 9035 LD ($85D3),HL Save Willy's new attribute buffer coordinates (in HL) at 85D3
90AD XOR A
90AE LD ($85D2),A ;
90B1 LD A,B ; 9038 LD A,B Save Willy's new y-coordinate at 85CF ;
90B2 LD ($85CF),A ; 9039 LD ($85CF),A
90B5 RET ; 903C LD A,$03 Change Willy's animation frame at 85D2 from 0 to 3
; 903E LD ($85D2),A
; 9041 RET
;=============================================
The above code laid out with symatry - NOTE the bug can be inserted by just removing the head check.
Here I relay out the code with symetry
Used by the routines at 8DD3 and 8ED4. This routine moves Willy left or right if necessary.
8FC2:
LD A,($85D6) Pick up the rope status indicator from 85D6
DEC A Is Willy on a rope?
RET m Return if so (Willy's movement along a rope is handled at 935E)
LD A,($85D0) Pick up Willy's direction and movement flags from 85D0
bit 1,a Is Willy moving left or right?
RET Z Return if not
bit 0,a Is Willy facing right?
;set up some data for later
LD A,($85D2) Pick up Willy's animation frame from 85D2
LD BC,$0000 set no displacement in bc
JP Z,rampR Jump if facing right
Code would drop through to rampL
Willy is moving right. ; Willy is moving left.
rampR: ;rampL
CP $03 OR A Is it 0?
JR Z,right ; JR Z,left If so, jump to move Willy's sprite left across a cell boundary
INC A ; DEC A Decrement Willy's animation frame at 85D2
LD ($85D2),A ; LD ($85D2),A
RET ; RET
Willy's sprite is moving right ; Willy's sprite is moving left across a cell boundary.
In the comments that follow, (x,y) refers to the
coordinates of the top-left cell currently occupied by Willy's sprite.
right: ; left
LD A,($85D1) LD A,($85D1) Pick up the airborne status indicator from 85D1
OR A ; OR A Is Willy jumping?
JR NZ,nrampR ; JR NZ,nrampL Jump if so - NO RAMP ADJUSTMENT
LD HL,($85D3) ; LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
LD A,($80DA) ; LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
DEC A ; DEC A Now A=0x1F if the ramp goes up to the left, or 0x41 if it goes up to the right
OR $9D ; OR $A1
XOR $BF ; XOR $E0
LD E,A ; LD E,A Point HL at the cell at (x-1,y+1) if the ramp goes up to the left, or at the cell at (x+1,y+2)
if the ramp goes up to the right
LD D,$00 ; LD D,$00
ADD HL,DE ; ADD HL,DE
; is the ramp undefoot ?
LD A,($80C4) ; LD A,($80C4) Pick up the attribute byte of the ramp tile for the current room from 80C4
CP (HL) ; CP (HL) Is there a ramp tile in the cell pointed to by HL?
JR NZ,nrampR ; JR NZ,nrampL Jump if not
; set bc for ramp downwards
LD BC,$0020 ; LD BC,$0020 Prepare BC for later addition
LD A,($80DA) ; LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
OR A ; OR A Does the ramp go up to the right?
JR Z,nrampR ; JR NZ,nrampL Jump if so
; set bc for ramp upwards
LD BC,$FFE0 ; LD BC,$FFE0 BC=-32 (the ramp goes up to the left)
; before going any further check for going off screen
nrampR: ;nrampL:
LD HL,($85D3) ; LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
; position adjust
INC HL ;
INC HL ;
LD A,L ; LD A,L Is Willy's screen x-coordinate 0 (on the far left)?
AND $1F ; AND $1F
JP Z,$949E ; JP Z,$948A If so, move Willy into the room to the left;
; the above jumped room at the left/right edge
; adjust position if on a ramp - i.e move up/down - note bc=0 if not on a ramp
add hl,bc ; ADD HL,BC this is the ramp adjustment
; re align the checking for walls
; DEC HL
ld de,$0020 ; LD DE,$0020 Displacement for the tile below
ld a,($80b2) ; LD A,($80B2) Pick up the attribute byte of the wall tile for the current room from 80B2
LD B,A ; LD B,A save wall tile value in b
; head check - to implement bug - remove the check - can do either left or right - perhaps both
CP (HL) ; CP (HL) Is there a wall tile in the cell pointed to by HL?
RET Z ; RET Z Return if so without moving Willy (his path is blocked)
; BODY CHECK
ADD HL,DE ; ADD HL,DE
CP (HL) ; CP (HL)
RET Z ; RET Z
;calc new y position
LD A,($85CF) ; LD A,($85CF) Pick up Willy's y-coordinate (Y) from 85CF
SRA C ; SRA C Now B=Y (if Willy is neither on nor about to step onto a ramp), or Y+16
(if Willy is walking down a ramp), or Y-16 (if Willy is on or about to step onto a ramp
that goes up to the left); this will be Willy's new y-coordinate
ADD A,C ; ADD A,C
LD c,A ; LD c,A
; now check if cell aligned
AND $0F ; AND $0F Is Willy at a point in a jump (left) where his sprite occupies three rows of cells?
JR Z,ramp3R ; JR Z,ramp3L Jump if not (Willy's sprite is cell-aligned)
; if not aligned check 3rd tile
LD A,B ; LD A,B
ADD HL,DE ; ADD HL,DE Point HL at the cell at (x-1,y+2)
CP (HL) ; CP (HL) Is there a wall tile there?
RET Z ; RET Z Return if so without moving Willy (his path is blocked)
OR A ; OR A Point HL at the cell at (x-1,y+1)
SBC HL,DE ; SBC HL,DE restore back to position before 3rd tile was checked
; adjust position back to level with the top tile
ramp3R: ;ramp3L:
OR A ; OR A
SBC HL,DE ; SBC HL,DE
;
; and re REALIGN for top left
DEC HL ;
; save data and exit
LD ($85D3),HL ; LD ($85D3),HL Save Willy's new attribute buffer coordinates (in HL) at 85D3
ld a,c ; LD A,c Get Willy's new y-coordinate
LD ($85CF),A ; LD ($85CF),A Save Willy's new y-coordinate at 85CF
xor a ; LD A,$03 Change Willy's animation frame at 85D2 from 0 to 3
ld ($85d2),a ; LD ($85D2),A
RET ; RET
;==============================================
The Feature that is displayed in the movement code.
When it was implemented it allowed a feature and that feature was used.
It is similar to the pause bug, attic arrow bug, missing and uncollectable objects etc
Whilst I think my code is correct - if I notice errors - then I will correct them. The purpose of the code is to show code being laid out as similar for both directions.
;
-
Norman Sword got a reaction from jetsetdanny in The Invisible Man
Because this would always be attributed to the original person. I have no incentive to add code to what (as far as I can see) is a simple deletion of the willy definition.
So in the words used on Dragons den "I'm out"
-------------------------------
path that could be taken - just not by me
1) To collide with the rope, Willy needs a definition. The deletion of Willies definition, means that path is out.
2) If the definition is intact
modify the code that draws willy - instead of actually putting the pixels to the screen- instead save the draw definition and the draw position, and return
in the rope draw routine - add a routine to use Willies draw definition and Willies draw position to xor Willy to the screen
Draw the rope - using xor - Willy will be flagged as collided in the normal way - movement on rope etc will still occur.
on rope exit add a routine to use Willies definition and Willies draw position to xor Willy off the screen.
The xor routine is a very simple sprite draw routine. Which would need adding,
The above allows Willy to interact with the rope....
The original modification was simply deleting Willies definition. This is adding ten times the effort of the original person to try and fix his hack.
Addendum:-
Just looked at this again - every reference to drawing willy elsewhere .. e.g the dancing Willies/ death screen etc. would need deleting.
-
Norman Sword got a reaction from jetsetdanny in MM Movement and Collision Detection explanation
A big post of z80 code
The reason for the left right anomaly is simply caused by poor code layout as done by Matthew.
When setting up movement code - it is normal to mirror the code for left and right. This simple procedure allows quick and accurate visual comparisons.
Here the first lot of code is the layout of checking left and right movement when possibly on a ramp
NOTE this has unused opcodes and does not mirror left and right
Expect visual changes - over time on what you can see here. I will probably edit the visual layout.
And correct errors as I see them.
MATTHEWS CODE:-
Used by the routines at 8DD3 and 8ED4. This routine moves Willy left or right if necessary.
8FBC LD A,($85D0) Pick up Willy's direction and movement flags from 85D0
8FBF AND $02 Is Willy moving left or right?
8FC1 RET Z Return if not
8FC2 LD A,($85D6) Pick up the rope status indicator from 85D6
8FC5 DEC A Is Willy on a rope?
8FC6 BIT 7,A
8FC8 RET Z Return if so (Willy's movement along a rope is handled at 935E)
8FC9 LD A,($85D0) Pick up Willy's direction and movement flags from 85D0
8FCC AND $01 Is Willy facing right?
8FCE JP Z,$9042 Jump if so
; LEFT AND RIGHT CODE - DISPLAYED NEXT TO EACH OTHER
Willy is moving right. ; Willy is moving left.
9042 LD A,($85D2) ; 8FD1 LD A,($85D2) Willy's animation frame from 85D2
9045 CP $03 ; 8FD4 OR A Is it 0?
9047 JR Z,$904E ; 8FD5 JR Z,$8FDC If so, jump to move Willy's sprite left across a cell boundary
9049 INC A ; 8FD7 DEC A Change Willy's animation frame at 85D2
904A LD ($85D2),A ;8FD8 LD ($85D2),A
904D RET ; 8FDB RET
Willy's sprite is moving right ; Willy's sprite is moving left across a cell boundary.
In the comments that follow, (x,y) refers to the coordinates of the top-left
cell currently occupied by Willy's sprite.
904E LD A,($85D1) ; 8FDC LD A,($85D1) Pick up the airborne status indicator from 85D1
9051 LD BC,$0000 ; 8FDF LD BC,$0000 Prepare BC for later addition
9054 OR A ; 8FE2 CP $00 Is Willy jumping?
9055 JR NZ,$9078 ; 8FE4 JR NZ,$900A Jump if so
9057 LD HL,($85D3) ; 8FE6 LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
; 8FE9 LD BC,$0000 Prepare BC for later addition (again, redundantly)
905A LD A,($80DA) ; 8FEC LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
905D DEC A ; 8FEF DEC A Now A=0x1F if the ramp goes up to the left, or 0x41 if it goes up to the right
905E OR $9D ; 8FF0 OR $A1
9060 XOR $BF ; 8FF2 XOR $E0
9062 LD E,A ; 8FF4 LD E,A Point HL at the cell at (x-1,y+1) if the ramp goes up to the left, or at the cell at
(x+1,y+2) if the ramp goes up to the right
9063 LD D,$00 ; 8FF5 LD D,$00
9065 ADD HL,DE ; 8FF7 ADD HL,DE
9066 LD A,($80C4) ; 8FF8 LD A,($80C4) Pick up the attribute byte of the ramp tile for the current room from 80C4
9069 CP (HL) ; 8FFB CP (HL) Is there a ramp tile in the cell pointed to by HL?
906A JR NZ,$9078 ; 8FFC JR NZ,$900A Jump if not
906C LD BC,$0020 ; 8FFE LD BC,$0020 Prepare BC for later addition
906F LD A,($80DA) ; 9001 LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
9072 OR A ; 9004 OR A Does the ramp go up to the right?
9073 JR Z,$9078 ; 9005 JR NZ,$900A Jump if so
9075 LD BC,$FFE0 ; 9007 LD BC,$FFE0 BC=-32 (the ramp goes up to the left)
9078 LD HL,($85D3) ; 900A LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
; check extremes far right ; and far left - jump room
907B ADD HL,BC ;
907C INC HL ;
907D INC HL ;
907E LD A,L ; 900D LD A,L Is Willy's screen x-coordinate 0 (on the far left)?
907F AND $1F ; 900E AND $1F
9081 JP Z,$949E ; 9010 JP Z,$948A If so, move Willy into the room to the left;
9084 LD DE,$0020 ;
9087 LD A,($80B2) ;
; 9013 ADD HL,BC Point HL at the cell at (x-1,y+1), or at the cell at (x-1,y) if Willy is on or about to step
onto a ramp that goes up to the left, or at the cell at (x-1,y+2) if Willy is walking down a ramp
; 9014 DEC HL
; 9015 LD DE,$0020
908A ADD HL,DE ; 9018 ADD HL,DE
; 9019 LD A,($80B2) Pick up the attribute byte of the wall tile for the current room from 80B2
908B CP (HL) ; 901C CP (HL) Is there a wall tile in the cell pointed to by HL?
908C RET Z ; 901D RET Z Return if so without moving Willy (his path is blocked)
908D LD A,($85CF) ; 901E LD A,($85CF) Pick up Willy's y-coordinate (Y) from 85CF
9090 SRA C ; 9021 SRA C Now B=Y (if Willy is neither on nor about to step onto a ramp), or Y+16
(if Willy is walking down a ramp),
or Y-16 (if Willy is on or about to step onto a ramp that goes up to the left)
this will be Willy's new y-coordinate
9092 ADD A,C ; 9023 ADD A,C
9093 LD B,A ; 9024 LD B,A
9094 AND $0F ; 9025 AND $0F Is Willy at a point in a jump (left) where his sprite occupies three rows of cells?
9096 JR Z,$90A1 ; 9027 JR Z,$9032 Jump if not (Willy's sprite is cell-aligned)
9098 LD A,($80B2) ; 9029 LD A,($80B2) Pick up the attribute byte of the wall tile for the current room from 80B2
909B ADD HL,DE ; 902C ADD HL,DE Point HL at the cell at (x-1,y+2)
909C CP (HL) ; 902D CP (HL) Is there a wall tile there?
909D RET Z ; 902E RET Z Return if so without moving Willy (his path is blocked)
909E OR A ; 902F OR A Point HL at the cell at (x-1,y+1)
909F SBC HL,DE ; 9030 SBC HL,DE
90A1 LD A,($80B2) ;
90A4 OR A ; 9032 OR A Point HL at the cell at (x-1,y), or at the cell at (x-1,y-1) if Willy is on or about
to step onto a ramp that goes up to the left, or at the cell at (x-1,y+1) if Willy
is walking down a ramp
90A5 SBC HL,DE ; 9033 SBC HL,DE
90A7 CP (HL) ;
90A8 RET Z ;
90A9 DEC HL ;
90AA LD ($85D3),HL ; 9035 LD ($85D3),HL Save Willy's new attribute buffer coordinates (in HL) at 85D3
90AD XOR A
90AE LD ($85D2),A ;
90B1 LD A,B ; 9038 LD A,B Save Willy's new y-coordinate at 85CF ;
90B2 LD ($85CF),A ; 9039 LD ($85CF),A
90B5 RET ; 903C LD A,$03 Change Willy's animation frame at 85D2 from 0 to 3
; 903E LD ($85D2),A
; 9041 RET
;=============================================
The above code laid out with symatry - NOTE the bug can be inserted by just removing the head check.
Here I relay out the code with symetry
Used by the routines at 8DD3 and 8ED4. This routine moves Willy left or right if necessary.
8FC2:
LD A,($85D6) Pick up the rope status indicator from 85D6
DEC A Is Willy on a rope?
RET m Return if so (Willy's movement along a rope is handled at 935E)
LD A,($85D0) Pick up Willy's direction and movement flags from 85D0
bit 1,a Is Willy moving left or right?
RET Z Return if not
bit 0,a Is Willy facing right?
;set up some data for later
LD A,($85D2) Pick up Willy's animation frame from 85D2
LD BC,$0000 set no displacement in bc
JP Z,rampR Jump if facing right
Code would drop through to rampL
Willy is moving right. ; Willy is moving left.
rampR: ;rampL
CP $03 OR A Is it 0?
JR Z,right ; JR Z,left If so, jump to move Willy's sprite left across a cell boundary
INC A ; DEC A Decrement Willy's animation frame at 85D2
LD ($85D2),A ; LD ($85D2),A
RET ; RET
Willy's sprite is moving right ; Willy's sprite is moving left across a cell boundary.
In the comments that follow, (x,y) refers to the
coordinates of the top-left cell currently occupied by Willy's sprite.
right: ; left
LD A,($85D1) LD A,($85D1) Pick up the airborne status indicator from 85D1
OR A ; OR A Is Willy jumping?
JR NZ,nrampR ; JR NZ,nrampL Jump if so - NO RAMP ADJUSTMENT
LD HL,($85D3) ; LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
LD A,($80DA) ; LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
DEC A ; DEC A Now A=0x1F if the ramp goes up to the left, or 0x41 if it goes up to the right
OR $9D ; OR $A1
XOR $BF ; XOR $E0
LD E,A ; LD E,A Point HL at the cell at (x-1,y+1) if the ramp goes up to the left, or at the cell at (x+1,y+2)
if the ramp goes up to the right
LD D,$00 ; LD D,$00
ADD HL,DE ; ADD HL,DE
; is the ramp undefoot ?
LD A,($80C4) ; LD A,($80C4) Pick up the attribute byte of the ramp tile for the current room from 80C4
CP (HL) ; CP (HL) Is there a ramp tile in the cell pointed to by HL?
JR NZ,nrampR ; JR NZ,nrampL Jump if not
; set bc for ramp downwards
LD BC,$0020 ; LD BC,$0020 Prepare BC for later addition
LD A,($80DA) ; LD A,($80DA) Pick up the direction byte of the ramp definition for the current room from 80DA
OR A ; OR A Does the ramp go up to the right?
JR Z,nrampR ; JR NZ,nrampL Jump if so
; set bc for ramp upwards
LD BC,$FFE0 ; LD BC,$FFE0 BC=-32 (the ramp goes up to the left)
; before going any further check for going off screen
nrampR: ;nrampL:
LD HL,($85D3) ; LD HL,($85D3) Collect Willy's attribute buffer coordinates from 85D3
; position adjust
INC HL ;
INC HL ;
LD A,L ; LD A,L Is Willy's screen x-coordinate 0 (on the far left)?
AND $1F ; AND $1F
JP Z,$949E ; JP Z,$948A If so, move Willy into the room to the left;
; the above jumped room at the left/right edge
; adjust position if on a ramp - i.e move up/down - note bc=0 if not on a ramp
add hl,bc ; ADD HL,BC this is the ramp adjustment
; re align the checking for walls
; DEC HL
ld de,$0020 ; LD DE,$0020 Displacement for the tile below
ld a,($80b2) ; LD A,($80B2) Pick up the attribute byte of the wall tile for the current room from 80B2
LD B,A ; LD B,A save wall tile value in b
; head check - to implement bug - remove the check - can do either left or right - perhaps both
CP (HL) ; CP (HL) Is there a wall tile in the cell pointed to by HL?
RET Z ; RET Z Return if so without moving Willy (his path is blocked)
; BODY CHECK
ADD HL,DE ; ADD HL,DE
CP (HL) ; CP (HL)
RET Z ; RET Z
;calc new y position
LD A,($85CF) ; LD A,($85CF) Pick up Willy's y-coordinate (Y) from 85CF
SRA C ; SRA C Now B=Y (if Willy is neither on nor about to step onto a ramp), or Y+16
(if Willy is walking down a ramp), or Y-16 (if Willy is on or about to step onto a ramp
that goes up to the left); this will be Willy's new y-coordinate
ADD A,C ; ADD A,C
LD c,A ; LD c,A
; now check if cell aligned
AND $0F ; AND $0F Is Willy at a point in a jump (left) where his sprite occupies three rows of cells?
JR Z,ramp3R ; JR Z,ramp3L Jump if not (Willy's sprite is cell-aligned)
; if not aligned check 3rd tile
LD A,B ; LD A,B
ADD HL,DE ; ADD HL,DE Point HL at the cell at (x-1,y+2)
CP (HL) ; CP (HL) Is there a wall tile there?
RET Z ; RET Z Return if so without moving Willy (his path is blocked)
OR A ; OR A Point HL at the cell at (x-1,y+1)
SBC HL,DE ; SBC HL,DE restore back to position before 3rd tile was checked
; adjust position back to level with the top tile
ramp3R: ;ramp3L:
OR A ; OR A
SBC HL,DE ; SBC HL,DE
;
; and re REALIGN for top left
DEC HL ;
; save data and exit
LD ($85D3),HL ; LD ($85D3),HL Save Willy's new attribute buffer coordinates (in HL) at 85D3
ld a,c ; LD A,c Get Willy's new y-coordinate
LD ($85CF),A ; LD ($85CF),A Save Willy's new y-coordinate at 85CF
xor a ; LD A,$03 Change Willy's animation frame at 85D2 from 0 to 3
ld ($85d2),a ; LD ($85D2),A
RET ; RET
;==============================================
The Feature that is displayed in the movement code.
When it was implemented it allowed a feature and that feature was used.
It is similar to the pause bug, attic arrow bug, missing and uncollectable objects etc
Whilst I think my code is correct - if I notice errors - then I will correct them. The purpose of the code is to show code being laid out as similar for both directions.
;
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Norman Sword got a reaction from jetsetdanny in MM Movement and Collision Detection explanation
See "altered reality" for corrected Willy movement. And it does not feel strange.
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Norman Sword got a reaction from Jet Set Willie in MM Movement and Collision Detection explanation
See "altered reality" for corrected Willy movement. And it does not feel strange.
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Norman Sword got a reaction from SymbolShift in MM Movement and Collision Detection explanation
See "altered reality" for corrected Willy movement. And it does not feel strange.
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Norman Sword got a reaction from Jet Set Willie in JSW with scrolling
Addendum - I wrote the cpc version of Jet Set Willy
The Title music is Moonlight Sonata and was writen by Beethoven in 1801. So slightly before Mr Wetheril came along.
The in game short tune is by Mr Wetheril.
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Norman Sword got a reaction from jetsetdanny in Embarrassing things
941C JR NZ,$940E 941E LD A,($85DE) Update the counter of items remaining at 85DE, and set the zero flag if there are no more items to collect 9421 INC A 9422 LD ($85DE),A 9425 JR NZ,$942C Jump if there are any items still to be collected 9427 LD A,$01 Update the game mode indicator at 85DF to 1 (all items collected) 9429 LD ($85DF),A 942C RES 6,(HL) Reset bit 6 of the first byte of the entry in the item table: the item has been collected 942E JR $9452 Jump to consider the next entry in the item table
The above (taken from a skoolkit dissasembly) shows that the variable #85de stores the playing games total amount of objects. - Start a game and change the value to #ff Then only 1 object is required to initiate the game over sequence. e.g. Maria will be gone and the jump on bed sequence can be done.
A more extensive change can be done by changing the initialisation routine. This change makes every game have only 1 object to complete.
8800 LD H,$A4 Page 0xA4 holds the first byte of each entry in the item table 8802 LD A,($A3FF) Pick up the index of the first item from A3FF 8805 LD L,A Point HL at the entry for the first item 8806 LD ($85DE),A Initialise the counter of items remaining at 85DE 8809 SET 6,(HL) Set the collection flag for every item in the item table
from the above it can be seen that the value at #a3ff holds the initilisation count for the objects. Setting this value to just #ff will force the game to have just one object. stored at #a4ff - Collect that one object and the can will be completed.
** NOTE. doing this does NOT remove the other objects from the object list. They still remain, but will not be active and will not be collectable
NOTE. the object stored at #a4ff needs to be close to the Maria screne so it can be collected easily. For example if placed in room #00 then that room will need to be visited to collect the one and one only object.
Whilst the above sets in motion a single object to collect, and initiate the game completed sequence. It is just as easy to initiate without collecting any objects.
From the first listing, it can be seen that a value of #01 is inserted into the location at #85df.
So start game and place a value of #1 into #85df. On entering the bedroom Maria will not be present and you can jump on the bed.
A very big note. The above is for JET SET WILLY as written by Matthew.
ADDENDUM.
** ignore this addendum. I was adding a point that is not important.