2018-08-13 22:17:36 +00:00
|
|
|
|
2016-12-16 01:21:51 +00:00
|
|
|
processor 6502
|
|
|
|
|
include "vcs.h"
|
|
|
|
|
include "macro.h"
|
|
|
|
|
include "xmacro.h"
|
|
|
|
|
|
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
|
|
|
|
|
|
seg.u Variables
|
|
|
|
|
org $80
|
|
|
|
|
|
|
|
|
|
Temp byte
|
|
|
|
|
PlyrXPos byte ; player X position
|
|
|
|
|
PlyrYPos byte ; player Y position
|
|
|
|
|
TrailFrac byte ; 8-bit fractional trail position
|
|
|
|
|
TrailPos word ; current 16-bit position along trail
|
|
|
|
|
Speed byte ; velocity along trail
|
|
|
|
|
Random word
|
|
|
|
|
PF1Mask byte
|
|
|
|
|
PF2Mask byte
|
|
|
|
|
YP0 byte ; sprite 0 vertical counter
|
|
|
|
|
YP1 byte ; sprite 1 vertical counter
|
|
|
|
|
SpritePtr0 word ; sprite 0 pointer
|
|
|
|
|
SpritePtr1 word ; sprite 1 pointer
|
|
|
|
|
YStop byte ; temp. register
|
|
|
|
|
NextHeight byte ; next sprite height
|
|
|
|
|
ObsIndex byte ; current obstacle index (0-7)
|
|
|
|
|
; Y offset into first obstacle
|
|
|
|
|
TrailObsYOffset byte
|
|
|
|
|
; next 8 bytes of trail data, starting from top of screen
|
|
|
|
|
TrailData ds 8
|
|
|
|
|
; Data for all 8 obstacle sprites
|
|
|
|
|
ObsXpos ds 8
|
|
|
|
|
ObsColor ds 8
|
|
|
|
|
ObsPtrLo ds 8
|
|
|
|
|
ObsPtrHi ds 8
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
SpriteHeight equ 20 ; Height of all sprites
|
|
|
|
|
TrailDisplayHeight equ 160 ; Height of trail dispaly area
|
|
|
|
|
|
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
|
|
|
|
|
|
seg Code
|
|
|
|
|
org $f000
|
|
|
|
|
|
|
|
|
|
Start
|
|
|
|
|
CLEAN_START
|
|
|
|
|
|
|
|
|
|
lda #1
|
|
|
|
|
sta Random
|
|
|
|
|
lda #70
|
|
|
|
|
sta PlyrXPos
|
|
|
|
|
|
|
|
|
|
lda #70
|
|
|
|
|
sta ObsXpos+0
|
|
|
|
|
lda #$7f
|
|
|
|
|
sta ObsColor+0
|
|
|
|
|
lda #<Frame0
|
|
|
|
|
sta ObsPtrLo+0
|
|
|
|
|
lda #>Frame0
|
|
|
|
|
sta ObsPtrHi+0
|
|
|
|
|
|
|
|
|
|
lda #40
|
|
|
|
|
sta ObsXpos+1
|
|
|
|
|
lda #$68
|
|
|
|
|
sta ObsColor+1
|
|
|
|
|
lda #<Frame0
|
|
|
|
|
sta ObsPtrLo+1
|
|
|
|
|
lda #>Frame0
|
|
|
|
|
sta ObsPtrHi+1
|
|
|
|
|
|
|
|
|
|
lda #60
|
|
|
|
|
sta ObsXpos+2
|
|
|
|
|
lda #$28
|
|
|
|
|
sta ObsColor+2
|
|
|
|
|
lda #<Frame0
|
|
|
|
|
sta ObsPtrLo+2
|
|
|
|
|
lda #>Frame0
|
|
|
|
|
sta ObsPtrHi+2
|
|
|
|
|
|
|
|
|
|
lda #$40
|
|
|
|
|
sta Speed
|
|
|
|
|
|
|
|
|
|
NextFrame
|
|
|
|
|
VERTICAL_SYNC
|
|
|
|
|
|
|
|
|
|
TIMER_SETUP 37
|
|
|
|
|
lda #150
|
|
|
|
|
sta YP0
|
|
|
|
|
lda #$ff
|
|
|
|
|
sta PF1Mask
|
|
|
|
|
lda #$0f
|
|
|
|
|
sta PF2Mask
|
|
|
|
|
lda #<Frame0
|
|
|
|
|
sta SpritePtr0
|
|
|
|
|
lda #>Frame0
|
|
|
|
|
sta SpritePtr0+1
|
|
|
|
|
lda #$ff
|
|
|
|
|
sta COLUP0
|
|
|
|
|
|
|
|
|
|
lda PlyrXPos
|
|
|
|
|
ldx #0
|
|
|
|
|
jsr SetHorizPos
|
|
|
|
|
sta WSYNC
|
|
|
|
|
sta HMOVE
|
|
|
|
|
|
|
|
|
|
TIMER_WAIT
|
|
|
|
|
|
|
|
|
|
TIMER_SETUP 192
|
|
|
|
|
jsr DrawTrail
|
|
|
|
|
TIMER_WAIT
|
|
|
|
|
|
|
|
|
|
TIMER_SETUP 30
|
|
|
|
|
jsr MoveAlongTrail
|
|
|
|
|
TIMER_WAIT
|
|
|
|
|
jmp NextFrame
|
|
|
|
|
|
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
|
|
|
|
|
|
; Move player along the trail
|
|
|
|
|
MoveAlongTrail subroutine
|
|
|
|
|
lda TrailFrac
|
|
|
|
|
sec
|
|
|
|
|
adc Speed
|
|
|
|
|
sta TrailFrac
|
|
|
|
|
php
|
|
|
|
|
lda TrailPos
|
|
|
|
|
adc #0
|
|
|
|
|
sta TrailPos
|
|
|
|
|
lda TrailPos+1
|
|
|
|
|
adc #0
|
|
|
|
|
sta TrailPos+1
|
|
|
|
|
plp
|
|
|
|
|
lda TrailObsYOffset
|
|
|
|
|
adc #0
|
|
|
|
|
cmp #SpriteHeight+4
|
|
|
|
|
bcc .NoNextObstacle
|
|
|
|
|
; Move obstacles up one slot
|
|
|
|
|
ldx #6
|
|
|
|
|
.MoveLoop
|
|
|
|
|
lda ObsXpos,x
|
|
|
|
|
sta ObsXpos+1,x
|
|
|
|
|
lda ObsColor,x
|
|
|
|
|
sta ObsColor+1,x
|
|
|
|
|
lda ObsPtrLo,x
|
|
|
|
|
sta ObsPtrLo+1,x
|
|
|
|
|
lda ObsPtrHi,x
|
|
|
|
|
sta ObsPtrHi+1,x
|
|
|
|
|
dex
|
|
|
|
|
bpl .MoveLoop
|
|
|
|
|
; Generate new obstacle
|
|
|
|
|
jsr NextRandom
|
|
|
|
|
sta ObsColor
|
|
|
|
|
and #$5f
|
|
|
|
|
sta ObsXpos
|
|
|
|
|
; Reset TrailObsYOffset
|
|
|
|
|
lda #0
|
|
|
|
|
.NoNextObstacle
|
|
|
|
|
sta TrailObsYOffset
|
|
|
|
|
rts
|
|
|
|
|
|
|
|
|
|
; Put the trail edges into the PF1 and PF2 registers.
|
|
|
|
|
; X = trail position lo byte
|
|
|
|
|
MAC TRAIL_PLAYFIELD
|
|
|
|
|
lda PF1Mask
|
|
|
|
|
and $f000,x
|
|
|
|
|
sta PF1
|
|
|
|
|
lda PF2Mask
|
|
|
|
|
and $f100,x
|
|
|
|
|
sta PF2
|
|
|
|
|
dex
|
|
|
|
|
ENDM
|
|
|
|
|
|
|
|
|
|
; Get next bitmap byte of sprite 0
|
|
|
|
|
MAC DRAW_SPRITE0
|
|
|
|
|
sec ; ensure carry set for subtraction
|
|
|
|
|
lda #SpriteHeight
|
|
|
|
|
isb YP0 ; INC yp0, then SBC yp0
|
|
|
|
|
tay
|
|
|
|
|
bcs .DoDraw ; outside bounds?
|
|
|
|
|
lda #0 ; clear bitmap
|
|
|
|
|
.byte $2c ; (BIT aaaa, skips next 2 bytes)
|
|
|
|
|
.DoDraw
|
|
|
|
|
lda (SpritePtr0),y ; lookup sprite bitmap
|
|
|
|
|
sta GRP0 ; A -> GRP0
|
|
|
|
|
ENDM
|
|
|
|
|
|
|
|
|
|
; Draw the trail
|
|
|
|
|
DrawTrail subroutine
|
|
|
|
|
lda TrailObsYOffset
|
|
|
|
|
sta NextHeight
|
|
|
|
|
lda #$c4
|
|
|
|
|
sta COLUPF
|
|
|
|
|
lda #$F0
|
|
|
|
|
sta PF0
|
|
|
|
|
lda #%0000001
|
|
|
|
|
sta CTRLPF
|
|
|
|
|
; lda #1
|
|
|
|
|
; sta VDELP0
|
|
|
|
|
; Set up ObsIndex (index of next obstacle to draw)
|
|
|
|
|
ldy #0
|
|
|
|
|
sty ObsIndex
|
|
|
|
|
; Set up X register with trail position lo byte,
|
|
|
|
|
; which displays the scrolling "forest" mask.
|
|
|
|
|
; We decrement this value every scanline and when it
|
|
|
|
|
; hits "YStop" we are done drawing.
|
|
|
|
|
lda TrailPos
|
|
|
|
|
sta YStop
|
|
|
|
|
clc
|
|
|
|
|
adc #TrailDisplayHeight
|
|
|
|
|
tax
|
|
|
|
|
; Set position of sprite
|
|
|
|
|
.SetSpritePos
|
|
|
|
|
sta HMCLR ; clear fine offsets
|
|
|
|
|
DRAW_SPRITE0
|
|
|
|
|
; Set up more values for sprite 1
|
|
|
|
|
ldy ObsIndex
|
|
|
|
|
lda ObsPtrLo,y
|
|
|
|
|
sta SpritePtr1
|
|
|
|
|
lda ObsPtrHi,y
|
|
|
|
|
sta SpritePtr1+1
|
|
|
|
|
lda ObsColor,y
|
|
|
|
|
sta COLUP1
|
|
|
|
|
; Update the playfield masks
|
|
|
|
|
; lda PFMask1,x
|
|
|
|
|
; sta PFMask1
|
|
|
|
|
; lda PFMask2,x
|
|
|
|
|
; sta PFMask2
|
|
|
|
|
; Set next height
|
|
|
|
|
lda NextHeight
|
|
|
|
|
sta YP1
|
|
|
|
|
lda #SpriteHeight
|
|
|
|
|
sta NextHeight
|
|
|
|
|
; Make sure grass texture is aligned
|
|
|
|
|
dex
|
|
|
|
|
cpx YStop
|
|
|
|
|
beq .NoMoreObjects
|
|
|
|
|
dex
|
|
|
|
|
cpx YStop
|
|
|
|
|
beq .NoMoreObjects
|
|
|
|
|
dex
|
|
|
|
|
cpx YStop
|
|
|
|
|
beq .NoMoreObjects
|
|
|
|
|
; Redraw sprite
|
|
|
|
|
DRAW_SPRITE0
|
|
|
|
|
; Position object horizontally
|
|
|
|
|
sta WSYNC
|
|
|
|
|
ldy ObsIndex
|
|
|
|
|
lda ObsXpos,y
|
|
|
|
|
iny
|
|
|
|
|
sty ObsIndex
|
|
|
|
|
sec
|
|
|
|
|
.DivideLoop
|
|
|
|
|
sbc #15 ; subtract 15
|
|
|
|
|
bcs .DivideLoop ; branch until negative
|
|
|
|
|
eor #7
|
|
|
|
|
asl
|
|
|
|
|
asl
|
|
|
|
|
asl
|
|
|
|
|
asl
|
|
|
|
|
sta HMP1 ; set fine offset
|
|
|
|
|
sta RESP1 ; fix coarse position
|
|
|
|
|
.Loop
|
|
|
|
|
sta WSYNC
|
|
|
|
|
; Draw sprite 0, with skipdraw
|
|
|
|
|
DRAW_SPRITE0
|
|
|
|
|
; Draw the playfield
|
|
|
|
|
TRAIL_PLAYFIELD
|
|
|
|
|
; Should we exit?
|
|
|
|
|
cpx YStop
|
|
|
|
|
beq .NoMoreObjects
|
|
|
|
|
; Draw sprite 1, no skipdraw
|
|
|
|
|
ldy YP1
|
|
|
|
|
lda (SpritePtr1),y
|
|
|
|
|
dey
|
|
|
|
|
sty YP1 ; YP1--
|
|
|
|
|
sta GRP1 ; A -> GRP1
|
|
|
|
|
; repeat until sprite 1 finished drawing (YP1<0)
|
|
|
|
|
bpl .Loop
|
|
|
|
|
; If not out of scanlines, position next sprite and continue
|
|
|
|
|
jmp .SetSpritePos
|
|
|
|
|
; Clean up playfield
|
|
|
|
|
.NoMoreObjects
|
|
|
|
|
lda #0
|
|
|
|
|
sta PF0
|
|
|
|
|
sta PF1
|
|
|
|
|
sta PF2
|
|
|
|
|
sta GRP0
|
|
|
|
|
sta GRP1
|
|
|
|
|
rts
|
|
|
|
|
|
|
|
|
|
; Random number generation
|
|
|
|
|
NextRandom subroutine
|
|
|
|
|
lda Random
|
|
|
|
|
lsr
|
|
|
|
|
ror Random+1
|
|
|
|
|
bcc .NoEor
|
|
|
|
|
eor #$d4
|
|
|
|
|
.NoEor:
|
|
|
|
|
sta Random
|
|
|
|
|
eor Random+1
|
|
|
|
|
rts
|
|
|
|
|
PrevRandom subroutine
|
|
|
|
|
lda Random
|
|
|
|
|
asl
|
|
|
|
|
rol Random+1
|
|
|
|
|
bcc .NoEor
|
|
|
|
|
eor #$a9
|
|
|
|
|
.NoEor:
|
|
|
|
|
sta Random
|
|
|
|
|
eor Random+1
|
|
|
|
|
rts
|
|
|
|
|
|
|
|
|
|
SetHorizPos
|
|
|
|
|
sta WSYNC ; start a new line
|
|
|
|
|
sec ; set carry flag
|
|
|
|
|
DivideLoop
|
|
|
|
|
sbc #15 ; subtract 15
|
|
|
|
|
bcs DivideLoop ; branch until negative
|
|
|
|
|
eor #7 ; calculate fine offset
|
|
|
|
|
asl
|
|
|
|
|
asl
|
|
|
|
|
asl
|
|
|
|
|
asl
|
|
|
|
|
sta HMP0,x ; set fine offset
|
|
|
|
|
sta RESP0,x ; fix coarse position
|
|
|
|
|
rts ; return to caller
|
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
|
|
|
|
|
|
align $100
|
|
|
|
|
PFMask1
|
|
|
|
|
byte #%00000000
|
|
|
|
|
byte #%10000000
|
|
|
|
|
byte #%11000000
|
|
|
|
|
byte #%11100000
|
|
|
|
|
byte #%11110000
|
|
|
|
|
byte #%11111000
|
|
|
|
|
byte #%11111100
|
|
|
|
|
byte #%11111110
|
|
|
|
|
byte #%11111111
|
|
|
|
|
byte #%11111111
|
|
|
|
|
byte #%11111111
|
|
|
|
|
byte #%11111111
|
|
|
|
|
byte #%11111111
|
|
|
|
|
byte #%11111111
|
|
|
|
|
byte #%11111111
|
|
|
|
|
byte #%11111111
|
|
|
|
|
byte #%11111111
|
|
|
|
|
PFMask2
|
|
|
|
|
byte #%00000000
|
|
|
|
|
byte #%00000000
|
|
|
|
|
byte #%00000000
|
|
|
|
|
byte #%00000000
|
|
|
|
|
byte #%00000000
|
|
|
|
|
byte #%00000000
|
|
|
|
|
byte #%00000000
|
|
|
|
|
byte #%00000000
|
|
|
|
|
byte #%00000001
|
|
|
|
|
byte #%00000011
|
|
|
|
|
byte #%00000111
|
|
|
|
|
byte #%00001111
|
|
|
|
|
byte #%00011111
|
|
|
|
|
byte #%00111111
|
|
|
|
|
byte #%01111111
|
|
|
|
|
byte #%11111111
|
|
|
|
|
|
|
|
|
|
; Bitmap data "standing" position
|
|
|
|
|
Frame0
|
|
|
|
|
.byte #0
|
|
|
|
|
.byte #%01101100;$F6
|
|
|
|
|
.byte #%00101000;$86
|
|
|
|
|
.byte #%00101000;$86
|
|
|
|
|
.byte #%00111000;$86
|
|
|
|
|
.byte #%10111010;$C2
|
|
|
|
|
.byte #%10111010;$C2
|
|
|
|
|
.byte #%01111100;$C2
|
|
|
|
|
.byte #%00111000;$C2
|
|
|
|
|
.byte #%00111000;$16
|
|
|
|
|
.byte #%01000100;$16
|
|
|
|
|
.byte #%01111100;$16
|
|
|
|
|
.byte #%01111100;$18
|
|
|
|
|
.byte #%01010100;$18
|
|
|
|
|
.byte #%01111100;$18
|
|
|
|
|
.byte #%11111110;$F2
|
|
|
|
|
.byte #%00111000;$F4
|
|
|
|
|
.byte 0,0,0,0,0,0,0
|
|
|
|
|
|
|
|
|
|
HMoveTable
|
|
|
|
|
hex 7060504030201000f0e0d0c0b0a09080
|
|
|
|
|
|
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
|
; Epilogue
|
|
|
|
|
org $fffc
|
|
|
|
|
.word Start
|
|
|
|
|
.word Start
|
