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Part 9 - ladder mechanics
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@ped7g
ped7g committed Feb 9, 2020
1 parent 35d9188 commit 42293f4
Showing 1 changed file with 156 additions and 18 deletions.
174 changes: 156 additions & 18 deletions SpecBong.asm
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,12 @@ mrx8 BYTE 0 ; PPPP Mx My Rt X8 (pal offset, mirrors, rotation, X8)
vpat BYTE 0 ; V 0 NNNNNN (visible, 5B type=off, pattern number 0..63)
ENDS

STRUCT S_LADDER_DATA
x BYTE 0 ; centre of ladder -8 (left edge of player sprite when aligned)
y BYTE 0 ; position of top platform -16 (Ypos for player to stand at top)
t BYTE 0 ; y+t = bottom platform -16 (Ypos for player to stand at)
ENDS

; selecting "Next" as virtual device in assembler, which allows me to set up all banks
; of Next (0..223 8kiB pages = 1.75MiB of memory) and page-in virtual memory
; with SLOT/PAGE/MMU directives
Expand Down Expand Up @@ -164,11 +170,10 @@ InitBallsLoop:
ld (ix+S_SPRITE_4B_ATTR.y),206 ; near bottom of paper area
ld (ix+S_SPRITE_4B_ATTR.mrx8),0 ; clear pal offset, mirrors, rotate, x8
ld (ix+S_SPRITE_4B_ATTR.vpat),$80 + 2 ; pattern "2" (player
;DEBUG position for testing the jump+fall mechanics
ld (ix+S_SPRITE_4B_ATTR.x),32+100
ld (ix+S_SPRITE_4B_ATTR.y),32
ld a,255
ld (Player1SafeLandingY),a
ld hl,0
ld (Player1LadderData),hl

; main loop of the game
GameLoop:
Expand Down Expand Up @@ -457,20 +462,30 @@ Player1MoveByControls:
ret

.notInTableJump:
; H = -16 + min(PlatformY[-3], PlatformY[+3]), C = extras of right platform, L = posX
ld a,(Player1Controls)
ld b,a ; keep control bits around in B for controls checks
; H = -16 + min(PlatformY[-3], PlatformY[+3]), C = extras of right platform, L = posX, B = controls

;-------------------------------------------------------------------------------------
; Part 9 - ladder mechanics - check if already hangs on ladder
ld de,(Player1LadderData) ; current ladder top+tall info (E=top,D=tall)
ld a,d
or a
jp nz,.isGrabbingLadder

; if landing pattern, turn it into normal pattern
ld a,(ix+S_SPRITE_4B_ATTR.vpat)
cp $80+4
jr nz,.notLandingSprite
ld (ix+S_SPRITE_4B_ATTR.vpat),$80 ; reset sprite to 0
.notLandingSprite:
;TODO if ladder pattern, do the ladder AI
jr c,.runningSprite
; landing pattern (or unhandled unknown state :) )
ld (ix+S_SPRITE_4B_ATTR.vpat),$80 ; reset sprite to 0 and continue with "running"
.runningSprite:
; if regular pattern, do regular movement handling
; check if stands at platform +-1px (and align with platform)
ld a,(ix+S_SPRITE_4B_ATTR.y)
sub h
adc a,0 ; turn -1/0/+1 into 0/+1
cp 2
inc a ; -1/0/+1 -> 0/+1/+2
cp 3
jr c,.almostAtPlatform
; too much above platform, turn it into freefall (table jump)
xor a
Expand All @@ -484,14 +499,18 @@ Player1MoveByControls:
ld a,18
add a,h
ld (Player1SafeLandingY),a
ld a,(Player1Controls)
ld b,a ; keep control bits around in B for simplicity
; C = extras of right platform, L = posX, B = user controls

bit JOY_BIT_FIRE,b
jr z,.notJumpPressed
; start a new jump sequence
ld a,$80+3 ; jump pattern + visible
ld (ix+S_SPRITE_4B_ATTR.vpat),a
xor a
bit JOY_BIT_UP,b ; up/down prevents the side jump
jr nz,.noRightJump
bit JOY_BIT_DOWN,b
jr nz,.noRightJump
bit JOY_BIT_LEFT,b
jr z,.noLeftJump
dec a
Expand All @@ -505,13 +524,106 @@ Player1MoveByControls:
jp .doTheTableJumpFall ; and do the first tick of jump this frame already

.notJumpPressed:
/* TODO
if up/down is pressed {
near ladder +-Npx -> switch to ladder pattern, adjust Y -> end
else reset dir controls + continue (stands)
}
*/
; C = extras of right platform, L = posX, B = user controls
; check if up/down is pressed during regular running -> may enter ladder or stand
ld a,b
and (1<<JOY_BIT_UP)|(1<<JOY_BIT_DOWN)
jp z,.noUpOrDownPressed
;-------------------------------------------------------------------------------------
; Part 9 - ladder mechanics - grab the near ladder if possible
bit 1,c ; check platform "extras" flag if ladder is near
ret z ; no ladder near, just keep standing
; check if some ladder can be grabbed by precise positions and controls pressed
ld c,LaddersCount+1
ld iy,LaddersData-S_LADDER_DATA
.LadderCheckLoop:
dec c
ret z ; no ladded is aligned enough, keep standing
ld de,S_LADDER_DATA
add iy,de ; advance pointer into ladder data
; check Y coordinates of ladder (top/bottom can be entered with correct key)
ld e,(iy+S_LADDER_DATA.y)
ld d,(iy+S_LADDER_DATA.t)
ld a,e
cp (ix+S_SPRITE_4B_ATTR.y)
jr nz,.notAtTopOfLadder
; if at top ladder position, check if control down is pressed and check X-coordinate
bit JOY_BIT_DOWN,b
jr z,.LadderCheckLoop ; not pressing "down", ignore it
jr .checkLadderXCoord
.notAtTopOfLadder:
add a,d
cp (ix+S_SPRITE_4B_ATTR.y)
jr nz,.LadderCheckLoop ; not at bottom position of ladder, ignore it
bit JOY_BIT_UP,b
jr z,.LadderCheckLoop ; not pressing "up", ignore it
.checkLadderXCoord:
ld h,(iy+S_LADDER_DATA.x)
ld a,h
sub l
add a,2 ; -2..+2 -> 0..+4
cp 5
jr nc,.LadderCheckLoop ; this ladder is more than +-2px away -> ignore it
; grab the ladder
ld l,h ; refresh also local copy of posX in L
ld (ix+S_SPRITE_4B_ATTR.x),l ; align with ladder on X-axis
ld (Player1LadderData),de ; current top+tall info
; following is regular ladder AI, after it was grabbed previously
.isGrabbingLadder:
; modify posY by controls
ld a,(TotalFrames)
and 1 ; only 2 of 4 frames the inputs are read
ld a,(ix+S_SPRITE_4B_ATTR.y)
jr z,.notClimbing ; but do the rest of ladder handler to set pattern/etc
bit JOY_BIT_DOWN,b
jr z,.notDescending
inc a
.notDescending:
bit JOY_BIT_UP,b
jr z,.notClimbing
dec a
.notClimbing:
; sanitize the posY
sub e
adc a,0 ; A=0..tall+1 where he is on the ladder (-1 fixed by ADC)
jr z,.atTopOrBottom
dec a
cp d ; Fc=(A-1) - tall (will be "no-carry" only when posY==tall+1)
adc a,0 ; clamps A to 0..tall range only
cp d
jr z,.atTopOrBottom
; somewhere in the middle of ladder, convert 1..tall-1 position into sprite pattern and posY
add a,e
ld (ix+S_SPRITE_4B_ATTR.y),a
sub e
cp LadderPatternDataSZ
jr c,.getClimbPatternFromTable
; beyond pre-defined table, so wrap around the last 8 patterns
and LadderPatternWrapMask
add a,LadderPatternWrapOfs
.getClimbPatternFromTable:
ld de,LadderPatternData
add de,a
ld a,(de)
ld (ix+S_SPRITE_4B_ATTR.vpat),a
ret

.atTopOrBottom:
add a,e
ld (ix+S_SPRITE_4B_ATTR.y),a
ld (ix+S_SPRITE_4B_ATTR.vpat),$80+10 ; standing pattern
ld a,b
and (1<<JOY_BIT_LEFT)|(1<<JOY_BIT_RIGHT)
ret z ; no left/right controls, stay on ladder standing
; player wants to leave the ladder, clear the current ladder data
xor a
ld (Player1LadderData+1),a ; clear the "tall" value to zero
; follow with regular running handler, that will resolve pattern/etc (L is up to date)
; |
; v

.noUpOrDownPressed:
; L = posX, B = user controls
bit JOY_BIT_LEFT,b
jr z,.notGoingLeft
; move left
Expand Down Expand Up @@ -713,6 +825,32 @@ Player1JumpDir:
DB 0 ; -1/0/+1 depending if the jump has direction or not
Player1SafeLandingY:
DB 0 ; last known safe landing Y (will be +18 to current Y when *at* platform)
Player1LadderData:
DB 0, 0 ; topY, tall (zero tall when not at ladder)

;-------------------------------------------------------------------------------------
; Part 9 - ladder mechanics - data of ladder positions and size

; ladders (256x192 positions in BMP):
; [152,163,185], [40,134,156], [152,105,127], [40,75,98], [152,46,68], [96, 19, 43]
LaddersData: ; adjustments: "32+" for sprite coordinates, "-8" and "-16" to adjust by player size
S_LADDER_DATA {32+152-8, 32+163-16, 185-163}
S_LADDER_DATA {32+40-8, 32+134-16, 156-134}
S_LADDER_DATA {32+152-8, 32+105-16, 127-105}
S_LADDER_DATA {32+40-8, 32+75-16, 98-75}
S_LADDER_DATA {32+152-8, 32+46-16, 68-46}
S_LADDER_DATA {32+96-8, 32+19-16, 43-19}
LaddersCount: EQU ($-LaddersData)/S_LADDER_DATA

LadderPatternData:
; +0..+7 -> standing + climbing at top
DB $80+10, $80+9, $80+9, $80+9, $80+9, $80+9, $80+9, $80+9
DB $80+8, $80+8, $80+8, $80+8, $80+8, $80+8, $80+8, $80+8
; +16..+23 -> regular climbing
DB $80+6, $80+6, $80+6, $80+6, $80+7, $80+7, $80+7, $80+7
LadderPatternDataSZ: EQU $ - LadderPatternData
LadderPatternWrapMask: EQU 7
LadderPatternWrapOfs: EQU 16

; reserve full 128 sprites 4B type (this demo will not use 5B type sprites)
ALIGN 256 ; aligned at 256B boundary w/o particular reason (yet)
Expand Down

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