Reorganized code with statuses, to introduce an intro scene.
Added routine to print text during intro; things needs to be developed.
This commit is contained in:
parent
7d8233fde2
commit
1d7226df45
203
snake.asm
203
snake.asm
@ -4,10 +4,17 @@
|
||||
; ----------------------------------------------------------------------
|
||||
|
||||
; Where is the snake head in video memory? Do math to calculate address
|
||||
; using $a0-$a1
|
||||
; using pointer at $a0-$a1
|
||||
tileMem = $a0
|
||||
|
||||
; Pointer to status string ($a3-$a4)
|
||||
printStatusString = $a3
|
||||
|
||||
; Pointer to intro string ($a3-$a4)
|
||||
printIntroString = $a3
|
||||
; Pointer to screen position where to print intro string ($fb-$fc)
|
||||
introScreenStart = $fb
|
||||
|
||||
org $801
|
||||
. = $801 ; 10 SYS9216 ($2400) BASIC autostart
|
||||
BYTE #$0b,#$08,#$0a,#$00,#$9e,#$39,#$32,#$31,#$36,#$00,#$00,#$00
|
||||
@ -54,10 +61,14 @@ length:
|
||||
random:
|
||||
BYTE
|
||||
|
||||
; Status (0 intro playing, 1 game running)
|
||||
; Status (0 fist time intro playing, 1 init (title) screen, 2 game running)
|
||||
status:
|
||||
BYTE
|
||||
|
||||
; Intro counter
|
||||
introCounter:
|
||||
BYTE
|
||||
|
||||
; Costants
|
||||
; ----------------------------------------------------------------------
|
||||
|
||||
@ -78,6 +89,9 @@ foodColor:
|
||||
gameoverString:
|
||||
BYTE "GAME IS OVER"
|
||||
BYTE #0
|
||||
intro0string:
|
||||
BYTE "SNAKE BY GIOMBA"
|
||||
BYTE #0
|
||||
|
||||
; List
|
||||
; ----------------------------------------------------------------------
|
||||
@ -94,23 +108,6 @@ start:
|
||||
; Clear screen, initialize keyboard, restore interrupts
|
||||
jsr $ff81
|
||||
|
||||
; Set screen colors
|
||||
; - - - - - - - - -
|
||||
lda #12
|
||||
sta $d020 ; overscan
|
||||
lda #9
|
||||
sta $d021 ; center
|
||||
; Upper bar -- fill with reversed spaces, color yellow
|
||||
ldx #39
|
||||
upperbarLoop:
|
||||
lda #$a0 ; reversed color space
|
||||
sta $400,x
|
||||
lda #7
|
||||
sta $d800,x
|
||||
dex
|
||||
cpx #$ff
|
||||
bne upperbarLoop
|
||||
|
||||
; Disable all interrupts
|
||||
sei
|
||||
|
||||
@ -144,30 +141,26 @@ upperbarLoop:
|
||||
lda #0
|
||||
jsr sidtune
|
||||
|
||||
; Put first piece of food
|
||||
lda foodTile
|
||||
sta $500
|
||||
; Set status as first-time intro playing
|
||||
lda #0
|
||||
sta status
|
||||
|
||||
; Enable interrupts
|
||||
cli
|
||||
|
||||
jsr fullreset
|
||||
|
||||
; Simple intro
|
||||
intro:
|
||||
ldx 53280
|
||||
inx
|
||||
stx 53280
|
||||
|
||||
intro0running:
|
||||
jsr $ffe4
|
||||
cmp #$20
|
||||
bne intro
|
||||
bne intro0running
|
||||
|
||||
lda #1
|
||||
; Set init variables of the game
|
||||
jsr fullreset
|
||||
; Set status as game playing
|
||||
lda #2
|
||||
sta status
|
||||
|
||||
endless:
|
||||
; Endless loop, show that there is enogh time after the interrupt
|
||||
; Endless loop, show that there is enough time after the interrupt
|
||||
ldx $400
|
||||
inx
|
||||
stx $400
|
||||
@ -176,6 +169,37 @@ endless:
|
||||
; Full reset
|
||||
; ----------------------------------------------------------------------
|
||||
fullreset:
|
||||
; Clear screen
|
||||
ldx #$ff
|
||||
lda #$20
|
||||
fullresetCLS:
|
||||
sta $400,x
|
||||
sta $500,x
|
||||
sta $600,x
|
||||
sta $700,x
|
||||
dex
|
||||
cpx #$ff
|
||||
bne fullresetCLS
|
||||
|
||||
; Set screen colors
|
||||
lda #12
|
||||
sta $d020 ; overscan
|
||||
lda #9
|
||||
sta $d021 ; center
|
||||
; Upper bar -- fill with reversed spaces, color yellow
|
||||
ldx #39
|
||||
upperbarLoop:
|
||||
lda #$a0 ; reversed color space
|
||||
sta $400,x
|
||||
lda #7
|
||||
sta $d800,x
|
||||
dex
|
||||
cpx #$ff
|
||||
bne upperbarLoop
|
||||
|
||||
; Init game variables
|
||||
lda foodTile
|
||||
sta $500 ; Put first piece of food
|
||||
lda #4
|
||||
sta irqn
|
||||
lda #6
|
||||
@ -188,29 +212,85 @@ fullreset:
|
||||
sta listStart
|
||||
lda #5
|
||||
sta length
|
||||
lda #0
|
||||
sta status
|
||||
|
||||
rts
|
||||
|
||||
; Interrupt Handler
|
||||
; ----------------------------------------------------------------------
|
||||
irq:
|
||||
; Things that must be done every interrupt (50Hz)
|
||||
; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
|
||||
; Acknoweledge IRQ
|
||||
dec $d019
|
||||
|
||||
; Save registers in stack
|
||||
pha
|
||||
txa
|
||||
pha
|
||||
tya
|
||||
pha
|
||||
|
||||
; Check status
|
||||
lda status
|
||||
cmp #0
|
||||
bne checkStatus1
|
||||
jsr status0
|
||||
jmp checkEndStatus
|
||||
checkStatus1:
|
||||
cmp #1
|
||||
beq doGame ; if status is 1, must do game
|
||||
jmp irqalways ; else simply do every-interrupt tasks (always-do)
|
||||
bne checkStatus2
|
||||
jsr status1
|
||||
jmp checkEndStatus
|
||||
checkStatus2
|
||||
cmp #2
|
||||
bne checkEndStatus
|
||||
jsr status2
|
||||
jmp checkEndStatus
|
||||
checkEndStatus:
|
||||
|
||||
doGame:
|
||||
; Play music
|
||||
jsr sidtune + 3
|
||||
|
||||
; Increase random value
|
||||
ldx random
|
||||
inx
|
||||
stx random
|
||||
|
||||
; Restore registers from stack
|
||||
pla
|
||||
tay
|
||||
pla
|
||||
tax
|
||||
pla
|
||||
|
||||
; Go to original system routine
|
||||
jmp $ea31
|
||||
|
||||
status0:
|
||||
status1:
|
||||
lda #<intro0string
|
||||
sta printIntroString
|
||||
lda #>intro0string
|
||||
sta printIntroString + 1
|
||||
lda #$00
|
||||
sta introScreenStart
|
||||
lda #$05
|
||||
sta introScreenStart + 1
|
||||
jsr printIntro
|
||||
|
||||
ldx $401
|
||||
inx
|
||||
stx $401
|
||||
rts
|
||||
|
||||
status2: ; do Game
|
||||
; Check counter
|
||||
ldx irqn
|
||||
dex
|
||||
stx irqn
|
||||
beq irqsometime ; if counter is 0, then do these "rare" things
|
||||
jmp irqalways ; else skip this section, and go to always-do interrupt routine
|
||||
beq irqsometime ; if counter is 0, then do these "rare" things
|
||||
rts ; else do nothing and simply return
|
||||
; as you can see, game actually runs at 12 Hz
|
||||
|
||||
irqsometime:
|
||||
; Things that must be done only one in four interrupts (12 Hz)
|
||||
@ -396,14 +476,6 @@ foodOK:
|
||||
lda calcTileY
|
||||
jsr printByte
|
||||
|
||||
; debug -- print snake head X,Y
|
||||
ldy #$1f
|
||||
lda snakeX
|
||||
jsr printByte
|
||||
ldy #$22
|
||||
lda snakeY
|
||||
jsr printByte
|
||||
|
||||
ldy #0
|
||||
jsr calcTileMem ; calc food address in memory
|
||||
lda (tileMem),y ; check if memory is empty
|
||||
@ -464,22 +536,7 @@ checkEndSelfEat:
|
||||
|
||||
skipPauseTests:
|
||||
|
||||
irqalways:
|
||||
; Things that must be done every interrupt (50Hz)
|
||||
; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
|
||||
|
||||
; Play music
|
||||
jsr sidtune + 3
|
||||
|
||||
; Increase random value
|
||||
ldx random
|
||||
inx
|
||||
stx random
|
||||
|
||||
; Go to original system routine
|
||||
jmp $ea31
|
||||
|
||||
brk
|
||||
rts
|
||||
|
||||
; Game is over
|
||||
; ----------------------------------------------------------------------
|
||||
@ -611,3 +668,21 @@ printStatusSkipSpace:
|
||||
jmp printStatusLoop
|
||||
printStatusEnd:
|
||||
rts
|
||||
|
||||
; Print string for intro
|
||||
printIntro:
|
||||
ldy #0
|
||||
printIntroLoop:
|
||||
lda (printIntroString),y
|
||||
beq printIntroEnd
|
||||
cmp #$20
|
||||
bne printIntroSkipSpace
|
||||
lda #$60
|
||||
printIntroSkipSpace:
|
||||
sec
|
||||
sbc #$40
|
||||
sta (introScreenStart),y
|
||||
iny
|
||||
jmp printIntroLoop
|
||||
printIntroEnd:
|
||||
rts
|
||||
|
||||
Loading…
Reference in New Issue
Block a user