Big memory and repository reorganization
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6
Makefile
6
Makefile
@ -1,8 +1,8 @@
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64:
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dasm snake.asm -DSYSTEM=64 -DDEBUG=0 -osnake.prg
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dasm main.asm -DSYSTEM=64 -DDEBUG=0 -osnake.prg
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debug:
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dasm snake.asm -DSYSTEM=64 -DDEBUG=1 -ssymbols.txt -osnake.prg
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dasm main.asm -DSYSTEM=64 -DDEBUG=1 -ssymbols.txt -osnake.prg
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16:
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dasm snake.asm -DSYSTEM=16 -osnake.prg
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dasm main.asm -DSYSTEM=16 -osnake.prg
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2
basic.asm
Normal file
2
basic.asm
Normal file
@ -0,0 +1,2 @@
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; 10 SYS10240 ($2800) BASIC autostart
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BYTE #$0b,#$08,#$0a,#$00,#$9e,#$31,#$30,#$32,#$34,#$30,#$00,#$00,#$00
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53
data.asm
Normal file
53
data.asm
Normal file
@ -0,0 +1,53 @@
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; Data section
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; ----------------------------------------------------------------------
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; Number of interrupt
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; Used as counter to be decremented to do some things less frequently
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irqn:
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BYTE
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; Direction of the snake (2,4,6,8 as down,left,right,up)
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; 5 means `pause`
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direction:
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BYTE
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; Snake head coordinates in video memory
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snakeX:
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BYTE
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snakeY:
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BYTE
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; Parameters for calcTileMem
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calcTileX:
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BYTE
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calcTileY:
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BYTE
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; List start and length
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listStart:
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BYTE
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length:
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BYTE
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; Random value
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random:
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BYTE
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; Status
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status:
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BYTE
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; Intro counter
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introCounter:
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BYTE #$4
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; Intro string x position, and next increment
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introX:
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BYTE #$0
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introXinc:
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BYTE #$1
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; Outro delay
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outroDelay
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BYTE #$ff
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314
game.asm
Normal file
314
game.asm
Normal file
@ -0,0 +1,314 @@
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statusPlay: ; do Game
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; Check counter
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ldx irqn
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dex
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stx irqn
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beq irqsometime ; if counter is 0, then do these "rare" things
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rts ; else do nothing and simply return
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; as you can see, game actually runs at 12 Hz
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irqsometime:
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; Things that must be done only one in four interrupts (12 Hz)
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; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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; If I am here, counter reached 0, so first reset it
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ldx #4
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stx irqn
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; Get pressed key and decide snake direction
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jsr $ffe4 ; Kernal routine GETIN
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cmp #0
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beq keybEndCheck ; if no key pressed, just skip this switch-case
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ldx #$7f ; else, if key pressed, reset random variable
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stx random
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keybCheckA: ; check for press of key `A`
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cmp #$41
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bne keybCheckS ; if not pressed `A`, just skip to next key to check
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lda direction ; else check if current direction is right
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cmp #6
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beq keybEndCheck ; if yes, you can't turn over yourself, so just skip to next key check
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lda #4
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sta direction ; else set direction to left and store new value
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jmp keybEndCheck ; skip all other key tests
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keybCheckS: ; simply re-do for S, D, W and other keys...
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cmp #$53
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bne keybCheckD
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lda direction
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cmp #8
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beq keybEndCheck
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lda #2
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sta direction
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jmp keybEndCheck
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keybCheckD:
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cmp #$44
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bne keybCheckW
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lda direction
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cmp #4
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beq keybEndCheck
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lda #6
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sta direction
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jmp keybEndCheck
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keybCheckW:
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cmp #$57
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bne keybCheckP
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lda direction
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cmp #2
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beq keybEndCheck
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lda #8
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sta direction
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jmp keybEndCheck
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keybCheckP:
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cmp #$50
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bne keybEndCheck
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lda #5
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sta direction
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jmp keybEndCheck
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keybEndCheck:
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; Get joystick status and decide snake direction
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; Joystick register bits 4:0 => Fire,Right,Left,Down,Up
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; 0 = Pressed; 1 = Idle
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lda $dc00 ; CIA joystick port 2 register
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ror ; rotate bit and put bit#0 in CF
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tax ; store byte value for next key check
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bcs joyCheckDown ; if CF = 1, then key was not depressed, so skip and check next...
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; ... else key was depressed!
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lda direction ; check for not overlapping direction (turn over yourself)
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cmp #2
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beq joyEndCheck
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lda #8
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sta direction
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jmp joyEndCheck
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joyCheckDown:
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txa
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ror
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tax
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bcs joyCheckLeft
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lda direction
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cmp #8
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beq joyEndCheck
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lda #2
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sta direction
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jmp joyEndCheck
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joyCheckLeft:
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txa
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ror
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tax
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bcs joyCheckRight
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lda direction
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cmp #6
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beq joyEndCheck
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lda #4
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sta direction
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jmp joyEndCheck
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joyCheckRight:
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txa
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ror
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tax
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bcs joyCheckFire
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lda direction
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cmp #4
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beq joyEndCheck
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lda #6
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sta direction
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jmp joyEndCheck
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joyCheckFire: ; `Fire` joystick key used to pause game
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txa
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ror
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tax
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bcs joyEndCheck
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lda #5
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sta direction
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joyEndCheck:
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; Get direction and move head accordingly
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lda direction
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dirCheck2: ; check if direction is down...
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cmp #2
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bne dirCheck4 ; if not down, then skip and check next direction,
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ldy snakeY ; else, direction is down, so get snakeY
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iny ; increment snakeY (keep in mind that screen up/down coordinates are reversed)
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sty snakeY ; update snakeY
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dirCheck4: ; simply re-do for other directions...
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cmp #4
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bne dirCheck6
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ldx snakeX
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dex
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stx snakeX
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dirCheck6:
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cmp #6
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bne dirCheck8
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ldx snakeX
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inx
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stx snakeX
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dirCheck8:
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cmp #8
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bne dirCheck5
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ldy snakeY
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dey
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sty snakeY
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dirCheck5:
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cmp #5
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bne dirEndCheck
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jmp skipPauseTests
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dirEndCheck:
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; Check screen boundaries overflow
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lda snakeX
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cmp #40
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bne overCheckX0 ; if snakeX is not 40, then all ok, skip to next test
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lda #0 ; else, there is an overflow, so trespass screen border
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sta snakeX
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overCheckX0: ; simply re-do for every side of the screen
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lda snakeX
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cmp #$ff
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bne overCheckY1
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lda #39
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sta snakeX
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overCheckY1:
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lda snakeY
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cmp #25
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bne overCheckY0
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lda #1
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sta snakeY
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overCheckY0
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lda snakeY
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cmp #0
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bne overEndCheck
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lda #24
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sta snakeY
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overEndCheck:
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; Put new head coordinates in list
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ldy listStart
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lda snakeX
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sta listX,y
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lda snakeY
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sta listY,y
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iny
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sty listStart
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ldy #0
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; Check for food eat / wall hit / self-eat
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; - - - - - - - - - - - - - - - - - - - - - -
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; --- Food eat ---
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lda snakeX ; calc head location in memory
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sta calcTileX
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lda snakeY
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sta calcTileY
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jsr calcTileMem
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lda (tileMem),y ; read content of head memory location
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cmp #FOOD_TILE
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beq foodEaten ; if memory does contain food, then perform foodEaten actions,
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jmp checkSelfEat ; else just loooong jump to test if I ate myself
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foodEaten:
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ldx length ; else, increment snake length,
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inx
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stx length
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genFood:
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ldx random
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inx
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stx random
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txa
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genFoodX: ; calculate `random` modulo SCREEN_W
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sec
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sbc #SCREEN_W
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cmp #SCREEN_W
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bcs genFoodX
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sta calcTileX
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txa
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genFoodY: ; calculate `random` modulo 22 (22 = SCREEN_H - 1)
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sec
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sbc #22
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cmp #22
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bcs genFoodY
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clc ; add 1 because 1st line can not be used
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adc #1
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sta calcTileY
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; Now I have X and Y coordinate for food stored in calcTileX, calcTileY
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; and I must check it is not the location that I am going to overwrite
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; with the head in draw snake head...
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lda calcTileX
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cmp snakeX
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bne foodOK
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lda calcTileY
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cmp snakeY
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beq genFood
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foodOK:
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; debug -- print choosen X,Y for food
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; ldy #$18
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; lda calcTileX
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; jsr printByte
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; ldy #$1b
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; lda calcTileY
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; jsr printByte
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ldy #0
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jsr calcTileMem ; calc food address in memory
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lda (tileMem),y ; check if memory is empty
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cmp #$20 ; is there a space?
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bne genFood ; if not, must generate another number
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lda #FOOD_TILE ; else, just put that fucking piece of food there
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sta (tileMem),y
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lda #$d4
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clc
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adc tileMem + 1
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sta tileMem + 1
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lda #FOOD_COLOR
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sta (tileMem),y
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; print score at $10th column
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ldy #$10
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lda length
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jsr printByte
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jmp checkEndSelfEat
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checkEndFood:
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; --- Self eat ---
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checkSelfEat:
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cmp #SNAKE_TILE
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bne checkEndSelfEat
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jmp gameover
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checkEndSelfEat:
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; Draw snake head
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ldy #0
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lda snakeX ; calc char address in video memory, and put SNAKE_TILE
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sta calcTileX
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lda snakeY
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sta calcTileY
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jsr calcTileMem
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lda #SNAKE_TILE
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sta (tileMem),y
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lda #$d4 ; add #$d400 to previous address (obtain color memory
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clc ; correspondent), and put SNAKE_COLOR
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adc tileMem + 1
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sta tileMem + 1
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lda #SNAKE_COLOR
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sta (tileMem),y
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; Erase snake tail
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lda listStart ; take start of list, and subtract snake length,
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sec ; to obtain index of end of list
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sbc length
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tax ; use previous value as index in list, and calc video memory address
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lda listX,x
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sta calcTileX
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lda listY,x
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sta calcTileY
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jsr calcTileMem
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lda #$20 ; just put a space to erase snake tail tile
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sta (tileMem),y
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skipPauseTests:
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rts
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17
gameover.asm
Normal file
17
gameover.asm
Normal file
@ -0,0 +1,17 @@
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; Game is over
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; ----------------------------------------------------------------------
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gameover:
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lda #<gameoverString
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sta printStatusString
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lda #>gameoverString
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sta printStatusString + 1
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jsr printStatus
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; Set gameover and outro status
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lda #$ff
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sta outroDelay
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lda #ST_OUTRO
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sta status
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rts
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80
intro1.asm
Normal file
80
intro1.asm
Normal file
@ -0,0 +1,80 @@
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; Currently statusIntro0 is the same as statusIntro1
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; statusIntro1 has just been reserved for future use
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statusIntro0:
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statusIntro1:
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; Decrement interrupt divider for the intro
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ldx introCounter
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dex
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stx introCounter
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cpx #0
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beq status1do ; if divider is 0, then do status1do ...
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rts ; ... else just do nothing and return
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status1do:
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; Reset introCounter
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ldx #5
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stx introCounter
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; I want to print strings at different columns to make them
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; bounce across the screen, so take last introX and add introXinc,
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; then print string at that point. If introX is too far right, then
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; set introXinc as #$ff (equals -1) so next time introX will be
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; decremented by 1. And then, if introX is too far left, then
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; set introXinc as #$01 so next time will be moved to right again.
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lda introX
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clc
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adc introXinc ; this is #$01 or #$0ff, so actually it is +1 or -1
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sta introX
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cmp #19 ; am I too far right?
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beq status1setSX ; if yes, set SX (left)
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cmp #0 ; am I too far left?
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beq status1setDX ; if yes, set DX (right)
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jmp status1okset ; else do nothing (aka, next time re-use current
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; increment value)
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status1setDX:
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lda #$01 ; set introXinc as +1
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sta introXinc
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jmp status1okset
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status1setSX:
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lda #$ff ; set introXinc as -1
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sta introXinc
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jmp status1okset
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status1okset:
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; Print "SNAKE BY GIOMBA" (see above for pointer details)
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lda #<intro0string
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sta printIntroString
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lda #>intro0string
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sta printIntroString + 1
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; $0428 is 2nd line (previously filled with color shades by reset routine)
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lda #$28
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clc
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adc introX ; just add X, to make it look like it has moved
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sta introScreenStart
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lda #$04
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sta introScreenStart + 1
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jsr printIntro
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; Print "PRESS SPACE TO PLAY"
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lda #<intro1string
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sta printIntroString
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lda #>intro1string
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sta printIntroString + 1
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; $0478 is 4th line (previously filled with color shades by reset routine)
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; add #19, then sub introX will make it move to other way of 2nd line
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lda #$78
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clc
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adc #19 ; add #19
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sec
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sbc introX ; sub introX
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sta introScreenStart
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lda #$04
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sta introScreenStart + 1
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jsr printIntro
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; Some considerations on speed:
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; yes, maybe I should have put the string chars once in screen text memory
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; and then move it left and right. Should re-think about this.
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; For now, just return.
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rts
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57
introreset.asm
Normal file
57
introreset.asm
Normal file
@ -0,0 +1,57 @@
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; Intro reset
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; ----------------------------------------------------------------------
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introreset:
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jsr multicolorOff
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; Clear screen
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ldx #$ff
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lda #$20
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introresetCLS:
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sta $400,x
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sta $500,x
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sta $600,x
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sta $700,x
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dex
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cpx #$ff
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bne introresetCLS
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; Copy shade colors from costant table to color RAM for 2nd and 4th line of text
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ldx #39
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introresetColorShade
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lda colorshade,x
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sta $d828,x ; 2nd line
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sta $d878,x ; 4th line
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dex
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cpx #$ff
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bne introresetColorShade
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; Set screen colors
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lda #0
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sta $d020 ; overscan
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sta $d021 ; center
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; Print website
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lda #<intro2string ; lsb of string address
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sta printIntroString ; put into lsb of source pointer
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lda #>intro2string ; do the same for msb of string address
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sta printIntroString + 1 ; put into msb of source pointer
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lda #$26 ; this is lsb of address of 20th line
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sta introScreenStart ; put into lsb of dest pointer
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lda #$07 ; do the same for msb of adress of 20th line
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sta introScreenStart + 1 ; put into msb of dest pointer
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jsr printIntro ; print
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; Print Copyright
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lda #<intro3string ; the assembly is the same as above,
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||||
sta printIntroString ; just change string to be printed
|
||||
lda #>intro3string ; and line (21th line)
|
||||
sta printIntroString + 1
|
||||
lda #$58
|
||||
sta introScreenStart
|
||||
lda #$07
|
||||
sta introScreenStart + 1
|
||||
jsr printIntro
|
||||
|
||||
rts
|
||||
|
||||
|
||||
79
main.asm
Normal file
79
main.asm
Normal file
@ -0,0 +1,79 @@
|
||||
processor 6502
|
||||
|
||||
; Platform specific code
|
||||
; Code yet to be developed, example to use:
|
||||
; ----------------------------------------------------------------------
|
||||
#if SYSTEM = 64
|
||||
; Commodore64 specific code
|
||||
#else
|
||||
; Commodore16 specific code
|
||||
#endif
|
||||
|
||||
; Uninitialized zeropage segment
|
||||
SEG.U zeropageSegment
|
||||
org $02
|
||||
INCLUDE "zeropage.asm"
|
||||
|
||||
; Initialized segments
|
||||
SEG basicSegment
|
||||
org $801
|
||||
INCLUDE "basic.asm"
|
||||
|
||||
SEG dataSegment
|
||||
org $900
|
||||
INCLUDE "data.asm"
|
||||
INCLUDE "const.asm"
|
||||
|
||||
; List
|
||||
; ----------------------------------------------------------------------
|
||||
. = $e00
|
||||
listX:
|
||||
. = $f00
|
||||
listY:
|
||||
|
||||
; SID tune (previously properly cleaned, see HVSC)
|
||||
; ----------------------------------------------------------------------
|
||||
SEG sidSegment
|
||||
org $1000
|
||||
sidtune:
|
||||
INCBIN "amour.sid"
|
||||
#if DEBUG = 1
|
||||
ECHO "End of SIDtune. Space left: ",($2000 - .)
|
||||
#endif
|
||||
|
||||
; Font Data
|
||||
; ----------------------------------------------------------------------
|
||||
SEG tggsSegment
|
||||
org $2000
|
||||
; This binary data that defines the font is exactly 2kB long ($800)
|
||||
tggsFont:
|
||||
INCBIN "tggs.font"
|
||||
|
||||
; Include program
|
||||
; ----------------------------------------------------------------------
|
||||
SEG programSegment
|
||||
org $2800
|
||||
jmp start
|
||||
|
||||
INCLUDE "game.asm"
|
||||
INCLUDE "gameover.asm"
|
||||
INCLUDE "gamereset.asm"
|
||||
INCLUDE "introreset.asm"
|
||||
INCLUDE "intro1.asm"
|
||||
INCLUDE "multicolor.asm"
|
||||
INCLUDE "outro.asm"
|
||||
INCLUDE "program.asm"
|
||||
INCLUDE "subroutines.asm"
|
||||
|
||||
#if DEBUG = 1
|
||||
ECHO "Program ends at: ",.
|
||||
#endif
|
||||
|
||||
;
|
||||
; coded during december 2017
|
||||
; by giomba -- giomba at glgprograms.it
|
||||
; this software is free software and is distributed
|
||||
; under the terms of GNU GPL v3 license
|
||||
;
|
||||
|
||||
; vim: set expandtab tabstop=4 shiftwidth=4:
|
||||
16
outro.asm
Normal file
16
outro.asm
Normal file
@ -0,0 +1,16 @@
|
||||
; Decrement outroDelay, just to let player see her/his end screen
|
||||
; with score
|
||||
statusOutro:
|
||||
ldy outroDelay ; load outroDelay and decrement
|
||||
dey
|
||||
sty outroDelay
|
||||
cpy #0
|
||||
beq statusOutroEnd
|
||||
rts
|
||||
statusOutroEnd:
|
||||
; Set status as ST_END: this way, the loop out of this interrupt,
|
||||
; will know that we finished, and will play the intro again
|
||||
lda #ST_END
|
||||
sta status
|
||||
rts
|
||||
|
||||
170
program.asm
Normal file
170
program.asm
Normal file
@ -0,0 +1,170 @@
|
||||
; ENTRY OF PROGRAM
|
||||
; ----------------------------------------------------------------------
|
||||
start:
|
||||
; Clear screen, initialize keyboard, restore interrupts
|
||||
jsr $ff81
|
||||
|
||||
; Disable all interrupts
|
||||
sei
|
||||
|
||||
; Turn off CIA interrupts and (eventually) flush the pending queue
|
||||
ldy #$7f
|
||||
sty $dc0d
|
||||
sty $dd0d
|
||||
lda $dc0d
|
||||
lda $dd0d
|
||||
|
||||
; Set Interrupt Request Mask as we want IRQ by raster beam
|
||||
lda #$1
|
||||
sta $d01a
|
||||
|
||||
; Store in $314 address of our custom interrupt handler
|
||||
ldx #<irq ; least significant byte
|
||||
ldy #>irq ; most significant byte
|
||||
stx $314
|
||||
sty $315
|
||||
|
||||
; Set raster beam to trigger interrupt at row zero
|
||||
lda #$00
|
||||
sta $d012
|
||||
|
||||
; Bit#0 of $d011 is used as bit#9 of $d012, and must be zero
|
||||
lda $d011
|
||||
and #$7f
|
||||
sta $d011
|
||||
|
||||
; Initialize player for first song
|
||||
lda #0
|
||||
jsr sidtune
|
||||
|
||||
; Initialize MultiColor mode
|
||||
jsr multicolorInit
|
||||
|
||||
; Zero-fill zeropage variables
|
||||
lda #$0
|
||||
ldx #$90
|
||||
zeroFillZeroPage:
|
||||
dex
|
||||
sta $0,x
|
||||
cpx #$2
|
||||
bne zeroFillZeroPage
|
||||
|
||||
; Set status as first-time intro playing
|
||||
lda #ST_INTRO0
|
||||
sta status
|
||||
|
||||
; Enable interrupts
|
||||
cli
|
||||
|
||||
; Reset screen (and other parameters) to play intro
|
||||
jsr introreset
|
||||
|
||||
intro0running: ; Cycle here until SPACE or `Q` is pressed
|
||||
jsr $ffe4 ; GETIN
|
||||
cmp #$20 ; Is it SPACE?
|
||||
beq intro0end ; if yes, go to intro0end and start game (see)
|
||||
cmp #$51 ; Is it Q?
|
||||
bne intro0running ; If not, keep looping here,
|
||||
jmp $fce2 ; else, reset the computer
|
||||
|
||||
; Intro is finished, now it's time to start the proper game
|
||||
intro0end:
|
||||
; Pause everything in interrupt
|
||||
lda #ST_PAUSE
|
||||
sta status
|
||||
; Set init variables of the game
|
||||
jsr gamereset
|
||||
|
||||
; Set status as game playing
|
||||
lda #ST_PLAY
|
||||
sta status
|
||||
|
||||
endless:
|
||||
; Loop waiting for gameover
|
||||
lda status
|
||||
cmp #ST_END ; is status equal to end ?
|
||||
bne endless ; if not, just wait looping here, else...
|
||||
|
||||
jsr introreset ; reset variables for intro
|
||||
lda #ST_INTRO0
|
||||
sta status ; put machine into play intro status
|
||||
jmp intro0running ; and go there waiting for keypress
|
||||
|
||||
; Interrupt Handler
|
||||
; ----------------------------------------------------------------------
|
||||
irq:
|
||||
; Things that must be done every interrupt (50Hz)
|
||||
; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
|
||||
; Acknoweledge IRQ
|
||||
dec $d019
|
||||
|
||||
; Save registers in stack
|
||||
pha
|
||||
txa
|
||||
pha
|
||||
tya
|
||||
pha
|
||||
|
||||
#if DEBUG = 1
|
||||
; Change background to visually see the ISR timing
|
||||
lda #2
|
||||
sta $d020
|
||||
#endif
|
||||
|
||||
; Check status and call appropriate sub-routine
|
||||
; Sort of switch-case
|
||||
lda status
|
||||
cmp #ST_INTRO0
|
||||
bne checkStatus1
|
||||
jsr statusIntro0
|
||||
jmp checkEndStatus
|
||||
checkStatus1:
|
||||
cmp #ST_INTRO1
|
||||
bne checkStatus2
|
||||
jsr statusIntro1
|
||||
jmp checkEndStatus
|
||||
checkStatus2
|
||||
cmp #ST_PLAY
|
||||
bne checkStatus3
|
||||
jsr statusPlay
|
||||
jmp checkEndStatus
|
||||
checkStatus3
|
||||
cmp #ST_OUTRO
|
||||
bne checkEndStatus
|
||||
jsr statusOutro
|
||||
jmp checkEndStatus
|
||||
checkEndStatus:
|
||||
|
||||
#if DEBUG = 1
|
||||
; Change background to show how much time does music take for each interrupt
|
||||
lda #1
|
||||
sta $d020
|
||||
#endif
|
||||
|
||||
; Play music
|
||||
jsr sidtune + 3
|
||||
jsr sidtune + 3
|
||||
jsr sidtune + 3
|
||||
jsr sidtune + 3
|
||||
jsr sidtune + 3
|
||||
|
||||
; Increase random value
|
||||
inc random
|
||||
|
||||
#if DEBUG = 1
|
||||
; Change background back again to visally see ISR timing
|
||||
lda #11
|
||||
sta $d020
|
||||
#endif
|
||||
|
||||
; Restore registers from stack
|
||||
pla
|
||||
tay
|
||||
pla
|
||||
tax
|
||||
pla
|
||||
|
||||
; Go to original system routine
|
||||
jmp $ea31
|
||||
|
||||
|
||||
917
snake.asm
917
snake.asm
@ -1,917 +0,0 @@
|
||||
processor 6502
|
||||
|
||||
; Platform specific code
|
||||
; Code yet to be developed, example to use:
|
||||
; ----------------------------------------------------------------------
|
||||
#if SYSTEM = 64
|
||||
; Commodore64 specific code
|
||||
#else
|
||||
; Commodore16 specific code
|
||||
#endif
|
||||
|
||||
; Zero page utilities
|
||||
; ----------------------------------------------------------------------
|
||||
SEG.U zeropage
|
||||
org $02
|
||||
; Where is the snake head in video memory? Do math to calculate address
|
||||
; using pointer at tileMem,tileMem+1
|
||||
tileMem DS 2
|
||||
|
||||
; Pointer to status string
|
||||
printStatusString DS 2
|
||||
|
||||
; Pointer to intro string
|
||||
printIntroString DS 2
|
||||
; Pointer to screen position where to print intro string ($fb-$fc)
|
||||
introScreenStart DS 2
|
||||
|
||||
#if DEBUG = 1
|
||||
; Locations $90-$FF in zeropage are used by kernal
|
||||
ECHO "End of zeropage variables. Space left: ",($90 - .)
|
||||
#endif
|
||||
|
||||
SEG program
|
||||
org $801
|
||||
. = $801 ; 10 SYS10240 ($2800) BASIC autostart
|
||||
BYTE #$0b,#$08,#$0a,#$00,#$9e,#$31,#$30,#$32,#$34,#$30,#$00,#$00,#$00
|
||||
|
||||
; Data section
|
||||
; ----------------------------------------------------------------------
|
||||
; Number of interrupt
|
||||
; Used as counter to be decremented to do some things less frequently
|
||||
irqn:
|
||||
BYTE
|
||||
|
||||
; Direction of the snake (2,4,6,8 as down,left,right,up)
|
||||
; 5 means `pause`
|
||||
direction:
|
||||
BYTE
|
||||
|
||||
; Snake head coordinates in video memory
|
||||
snakeX:
|
||||
BYTE
|
||||
snakeY:
|
||||
BYTE
|
||||
|
||||
; Parameters for calcTileMem
|
||||
calcTileX:
|
||||
BYTE
|
||||
calcTileY:
|
||||
BYTE
|
||||
|
||||
; List start and length
|
||||
listStart:
|
||||
BYTE
|
||||
length:
|
||||
BYTE
|
||||
|
||||
; Random value
|
||||
random:
|
||||
BYTE
|
||||
|
||||
; Status
|
||||
status:
|
||||
BYTE
|
||||
|
||||
; Intro counter
|
||||
introCounter:
|
||||
BYTE #$4
|
||||
|
||||
; Intro string x position, and next increment
|
||||
introX:
|
||||
BYTE #$0
|
||||
introXinc:
|
||||
BYTE #$1
|
||||
|
||||
; Outro delay
|
||||
outroDelay
|
||||
BYTE #$ff
|
||||
|
||||
INCLUDE "cost.asm"
|
||||
|
||||
#if DEBUG = 1
|
||||
ECHO "End of Data. Space left: ",($e00 - .)
|
||||
#endif
|
||||
|
||||
; List
|
||||
; ----------------------------------------------------------------------
|
||||
. = $e00
|
||||
listX:
|
||||
. = $f00
|
||||
listY:
|
||||
|
||||
; SID tune (previously properly cleaned, see HVSC)
|
||||
; ----------------------------------------------------------------------
|
||||
. = $1000
|
||||
sidtune:
|
||||
INCBIN "amour.sid"
|
||||
#if DEBUG = 1
|
||||
ECHO "End of SIDtune. Space left: ",($2000 - .)
|
||||
#endif
|
||||
|
||||
. = $2000
|
||||
; This binary data that defines the font is exactly 2kB long ($800)
|
||||
tggsFont:
|
||||
INCBIN "tggs.font"
|
||||
|
||||
; ENTRY OF PROGRAM
|
||||
; ----------------------------------------------------------------------
|
||||
. = $2800
|
||||
start:
|
||||
; Clear screen, initialize keyboard, restore interrupts
|
||||
jsr $ff81
|
||||
|
||||
; Disable all interrupts
|
||||
sei
|
||||
|
||||
; Turn off CIA interrupts and (eventually) flush the pending queue
|
||||
ldy #$7f
|
||||
sty $dc0d
|
||||
sty $dd0d
|
||||
lda $dc0d
|
||||
lda $dd0d
|
||||
|
||||
; Set Interrupt Request Mask as we want IRQ by raster beam
|
||||
lda #$1
|
||||
sta $d01a
|
||||
|
||||
; Store in $314 address of our custom interrupt handler
|
||||
ldx #<irq ; least significant byte
|
||||
ldy #>irq ; most significant byte
|
||||
stx $314
|
||||
sty $315
|
||||
|
||||
; Set raster beam to trigger interrupt at row zero
|
||||
lda #$00
|
||||
sta $d012
|
||||
|
||||
; Bit#0 of $d011 is used as bit#9 of $d012, and must be zero
|
||||
lda $d011
|
||||
and #$7f
|
||||
sta $d011
|
||||
|
||||
; Initialize player for first song
|
||||
lda #0
|
||||
jsr sidtune
|
||||
|
||||
; Initialize MultiColor mode
|
||||
jsr multicolorInit
|
||||
|
||||
; Zero-fill zeropage variables
|
||||
lda #$0
|
||||
ldx #$90
|
||||
zeroFillZeroPage:
|
||||
dex
|
||||
sta $0,x
|
||||
cpx #$2
|
||||
bne zeroFillZeroPage
|
||||
|
||||
; Set status as first-time intro playing
|
||||
lda #ST_INTRO0
|
||||
sta status
|
||||
|
||||
; Enable interrupts
|
||||
cli
|
||||
|
||||
; Reset screen (and other parameters) to play intro
|
||||
jsr introreset
|
||||
|
||||
intro0running: ; Cycle here until SPACE or `Q` is pressed
|
||||
jsr $ffe4 ; GETIN
|
||||
cmp #$20 ; Is it SPACE?
|
||||
beq intro0end ; if yes, go to intro0end and start game (see)
|
||||
cmp #$51 ; Is it Q?
|
||||
bne intro0running ; If not, keep looping here,
|
||||
jmp $fce2 ; else, reset the computer
|
||||
|
||||
; Intro is finished, now it's time to start the proper game
|
||||
intro0end:
|
||||
; Pause everything in interrupt
|
||||
lda #ST_PAUSE
|
||||
sta status
|
||||
; Set init variables of the game
|
||||
jsr gamereset
|
||||
|
||||
; Set status as game playing
|
||||
lda #ST_PLAY
|
||||
sta status
|
||||
|
||||
endless:
|
||||
; Loop waiting for gameover
|
||||
lda status
|
||||
cmp #ST_END ; is status equal to end ?
|
||||
bne endless ; if not, just wait looping here, else...
|
||||
|
||||
jsr introreset ; reset variables for intro
|
||||
lda #ST_INTRO0
|
||||
sta status ; put machine into play intro status
|
||||
jmp intro0running ; and go there waiting for keypress
|
||||
|
||||
INCLUDE "gamereset.asm"
|
||||
|
||||
; Intro reset
|
||||
; ----------------------------------------------------------------------
|
||||
introreset:
|
||||
jsr multicolorOff
|
||||
|
||||
; Clear screen
|
||||
ldx #$ff
|
||||
lda #$20
|
||||
introresetCLS:
|
||||
sta $400,x
|
||||
sta $500,x
|
||||
sta $600,x
|
||||
sta $700,x
|
||||
dex
|
||||
cpx #$ff
|
||||
bne introresetCLS
|
||||
|
||||
; Copy shade colors from costant table to color RAM for 2nd and 4th line of text
|
||||
ldx #39
|
||||
introresetColorShade
|
||||
lda colorshade,x
|
||||
sta $d828,x ; 2nd line
|
||||
sta $d878,x ; 4th line
|
||||
dex
|
||||
cpx #$ff
|
||||
bne introresetColorShade
|
||||
|
||||
; Set screen colors
|
||||
lda #0
|
||||
sta $d020 ; overscan
|
||||
sta $d021 ; center
|
||||
|
||||
; Print website
|
||||
lda #<intro2string ; lsb of string address
|
||||
sta printIntroString ; put into lsb of source pointer
|
||||
lda #>intro2string ; do the same for msb of string address
|
||||
sta printIntroString + 1 ; put into msb of source pointer
|
||||
lda #$26 ; this is lsb of address of 20th line
|
||||
sta introScreenStart ; put into lsb of dest pointer
|
||||
lda #$07 ; do the same for msb of adress of 20th line
|
||||
sta introScreenStart + 1 ; put into msb of dest pointer
|
||||
jsr printIntro ; print
|
||||
|
||||
; Print Copyright
|
||||
lda #<intro3string ; the assembly is the same as above,
|
||||
sta printIntroString ; just change string to be printed
|
||||
lda #>intro3string ; and line (21th line)
|
||||
sta printIntroString + 1
|
||||
lda #$58
|
||||
sta introScreenStart
|
||||
lda #$07
|
||||
sta introScreenStart + 1
|
||||
jsr printIntro
|
||||
|
||||
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
|
||||
|
||||
#if DEBUG = 1
|
||||
; Change background to visually see the ISR timing
|
||||
lda #2
|
||||
sta $d020
|
||||
#endif
|
||||
|
||||
; Check status and call appropriate sub-routine
|
||||
; Sort of switch-case
|
||||
lda status
|
||||
cmp #ST_INTRO0
|
||||
bne checkStatus1
|
||||
jsr statusIntro0
|
||||
jmp checkEndStatus
|
||||
checkStatus1:
|
||||
cmp #ST_INTRO1
|
||||
bne checkStatus2
|
||||
jsr statusIntro1
|
||||
jmp checkEndStatus
|
||||
checkStatus2
|
||||
cmp #ST_PLAY
|
||||
bne checkStatus3
|
||||
jsr statusPlay
|
||||
jmp checkEndStatus
|
||||
checkStatus3
|
||||
cmp #ST_OUTRO
|
||||
bne checkEndStatus
|
||||
jsr statusOutro
|
||||
jmp checkEndStatus
|
||||
checkEndStatus:
|
||||
|
||||
#if DEBUG = 1
|
||||
; Change background to show how much time does music take for each interrupt
|
||||
lda #1
|
||||
sta $d020
|
||||
#endif
|
||||
|
||||
; Play music
|
||||
jsr sidtune + 3
|
||||
jsr sidtune + 3
|
||||
jsr sidtune + 3
|
||||
jsr sidtune + 3
|
||||
jsr sidtune + 3
|
||||
|
||||
; Increase random value
|
||||
inc random
|
||||
|
||||
#if DEBUG = 1
|
||||
; Change background back again to visally see ISR timing
|
||||
lda #11
|
||||
sta $d020
|
||||
#endif
|
||||
|
||||
; Restore registers from stack
|
||||
pla
|
||||
tay
|
||||
pla
|
||||
tax
|
||||
pla
|
||||
|
||||
; Go to original system routine
|
||||
jmp $ea31
|
||||
|
||||
; Currently statusIntro0 is the same as statusIntro1
|
||||
; statusIntro1 has just been reserved for future use
|
||||
statusIntro0:
|
||||
statusIntro1:
|
||||
; Decrement interrupt divider for the intro
|
||||
ldx introCounter
|
||||
dex
|
||||
stx introCounter
|
||||
cpx #0
|
||||
beq status1do ; if divider is 0, then do status1do ...
|
||||
rts ; ... else just do nothing and return
|
||||
status1do:
|
||||
; Reset introCounter
|
||||
ldx #5
|
||||
stx introCounter
|
||||
|
||||
; I want to print strings at different columns to make them
|
||||
; bounce across the screen, so take last introX and add introXinc,
|
||||
; then print string at that point. If introX is too far right, then
|
||||
; set introXinc as #$ff (equals -1) so next time introX will be
|
||||
; decremented by 1. And then, if introX is too far left, then
|
||||
; set introXinc as #$01 so next time will be moved to right again.
|
||||
lda introX
|
||||
clc
|
||||
adc introXinc ; this is #$01 or #$0ff, so actually it is +1 or -1
|
||||
sta introX
|
||||
cmp #19 ; am I too far right?
|
||||
beq status1setSX ; if yes, set SX (left)
|
||||
cmp #0 ; am I too far left?
|
||||
beq status1setDX ; if yes, set DX (right)
|
||||
jmp status1okset ; else do nothing (aka, next time re-use current
|
||||
; increment value)
|
||||
status1setDX:
|
||||
lda #$01 ; set introXinc as +1
|
||||
sta introXinc
|
||||
jmp status1okset
|
||||
status1setSX:
|
||||
lda #$ff ; set introXinc as -1
|
||||
sta introXinc
|
||||
jmp status1okset
|
||||
|
||||
status1okset:
|
||||
; Print "SNAKE BY GIOMBA" (see above for pointer details)
|
||||
lda #<intro0string
|
||||
sta printIntroString
|
||||
lda #>intro0string
|
||||
sta printIntroString + 1
|
||||
; $0428 is 2nd line (previously filled with color shades by reset routine)
|
||||
lda #$28
|
||||
clc
|
||||
adc introX ; just add X, to make it look like it has moved
|
||||
sta introScreenStart
|
||||
lda #$04
|
||||
sta introScreenStart + 1
|
||||
jsr printIntro
|
||||
|
||||
; Print "PRESS SPACE TO PLAY"
|
||||
lda #<intro1string
|
||||
sta printIntroString
|
||||
lda #>intro1string
|
||||
sta printIntroString + 1
|
||||
; $0478 is 4th line (previously filled with color shades by reset routine)
|
||||
; add #19, then sub introX will make it move to other way of 2nd line
|
||||
lda #$78
|
||||
clc
|
||||
adc #19 ; add #19
|
||||
sec
|
||||
sbc introX ; sub introX
|
||||
sta introScreenStart
|
||||
lda #$04
|
||||
sta introScreenStart + 1
|
||||
jsr printIntro
|
||||
|
||||
; Some considerations on speed:
|
||||
; yes, maybe I should have put the string chars once in screen text memory
|
||||
; and then move it left and right. Should re-think about this.
|
||||
; For now, just return.
|
||||
rts
|
||||
|
||||
statusPlay: ; do Game
|
||||
; Check counter
|
||||
ldx irqn
|
||||
dex
|
||||
stx irqn
|
||||
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)
|
||||
; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
|
||||
|
||||
; If I am here, counter reached 0, so first reset it
|
||||
ldx #4
|
||||
stx irqn
|
||||
|
||||
; Get pressed key and decide snake direction
|
||||
jsr $ffe4 ; Kernal routine GETIN
|
||||
cmp #0
|
||||
beq keybEndCheck ; if no key pressed, just skip this switch-case
|
||||
ldx #$7f ; else, if key pressed, reset random variable
|
||||
stx random
|
||||
keybCheckA: ; check for press of key `A`
|
||||
cmp #$41
|
||||
bne keybCheckS ; if not pressed `A`, just skip to next key to check
|
||||
lda direction ; else check if current direction is right
|
||||
cmp #6
|
||||
beq keybEndCheck ; if yes, you can't turn over yourself, so just skip to next key check
|
||||
lda #4
|
||||
sta direction ; else set direction to left and store new value
|
||||
jmp keybEndCheck ; skip all other key tests
|
||||
keybCheckS: ; simply re-do for S, D, W and other keys...
|
||||
cmp #$53
|
||||
bne keybCheckD
|
||||
lda direction
|
||||
cmp #8
|
||||
beq keybEndCheck
|
||||
lda #2
|
||||
sta direction
|
||||
jmp keybEndCheck
|
||||
keybCheckD:
|
||||
cmp #$44
|
||||
bne keybCheckW
|
||||
lda direction
|
||||
cmp #4
|
||||
beq keybEndCheck
|
||||
lda #6
|
||||
sta direction
|
||||
jmp keybEndCheck
|
||||
keybCheckW:
|
||||
cmp #$57
|
||||
bne keybCheckP
|
||||
lda direction
|
||||
cmp #2
|
||||
beq keybEndCheck
|
||||
lda #8
|
||||
sta direction
|
||||
jmp keybEndCheck
|
||||
keybCheckP:
|
||||
cmp #$50
|
||||
bne keybEndCheck
|
||||
lda #5
|
||||
sta direction
|
||||
jmp keybEndCheck
|
||||
keybEndCheck:
|
||||
|
||||
; Get joystick status and decide snake direction
|
||||
; Joystick register bits 4:0 => Fire,Right,Left,Down,Up
|
||||
; 0 = Pressed; 1 = Idle
|
||||
lda $dc00 ; CIA joystick port 2 register
|
||||
ror ; rotate bit and put bit#0 in CF
|
||||
tax ; store byte value for next key check
|
||||
bcs joyCheckDown ; if CF = 1, then key was not depressed, so skip and check next...
|
||||
; ... else key was depressed!
|
||||
lda direction ; check for not overlapping direction (turn over yourself)
|
||||
cmp #2
|
||||
beq joyEndCheck
|
||||
lda #8
|
||||
sta direction
|
||||
jmp joyEndCheck
|
||||
joyCheckDown:
|
||||
txa
|
||||
ror
|
||||
tax
|
||||
bcs joyCheckLeft
|
||||
lda direction
|
||||
cmp #8
|
||||
beq joyEndCheck
|
||||
lda #2
|
||||
sta direction
|
||||
jmp joyEndCheck
|
||||
joyCheckLeft:
|
||||
txa
|
||||
ror
|
||||
tax
|
||||
bcs joyCheckRight
|
||||
lda direction
|
||||
cmp #6
|
||||
beq joyEndCheck
|
||||
lda #4
|
||||
sta direction
|
||||
jmp joyEndCheck
|
||||
joyCheckRight:
|
||||
txa
|
||||
ror
|
||||
tax
|
||||
bcs joyCheckFire
|
||||
lda direction
|
||||
cmp #4
|
||||
beq joyEndCheck
|
||||
lda #6
|
||||
sta direction
|
||||
jmp joyEndCheck
|
||||
joyCheckFire: ; `Fire` joystick key used to pause game
|
||||
txa
|
||||
ror
|
||||
tax
|
||||
bcs joyEndCheck
|
||||
lda #5
|
||||
sta direction
|
||||
joyEndCheck:
|
||||
|
||||
; Get direction and move head accordingly
|
||||
lda direction
|
||||
dirCheck2: ; check if direction is down...
|
||||
cmp #2
|
||||
bne dirCheck4 ; if not down, then skip and check next direction,
|
||||
ldy snakeY ; else, direction is down, so get snakeY
|
||||
iny ; increment snakeY (keep in mind that screen up/down coordinates are reversed)
|
||||
sty snakeY ; update snakeY
|
||||
dirCheck4: ; simply re-do for other directions...
|
||||
cmp #4
|
||||
bne dirCheck6
|
||||
ldx snakeX
|
||||
dex
|
||||
stx snakeX
|
||||
dirCheck6:
|
||||
cmp #6
|
||||
bne dirCheck8
|
||||
ldx snakeX
|
||||
inx
|
||||
stx snakeX
|
||||
dirCheck8:
|
||||
cmp #8
|
||||
bne dirCheck5
|
||||
ldy snakeY
|
||||
dey
|
||||
sty snakeY
|
||||
dirCheck5:
|
||||
cmp #5
|
||||
bne dirEndCheck
|
||||
jmp skipPauseTests
|
||||
dirEndCheck:
|
||||
|
||||
; Check screen boundaries overflow
|
||||
lda snakeX
|
||||
cmp #40
|
||||
bne overCheckX0 ; if snakeX is not 40, then all ok, skip to next test
|
||||
lda #0 ; else, there is an overflow, so trespass screen border
|
||||
sta snakeX
|
||||
overCheckX0: ; simply re-do for every side of the screen
|
||||
lda snakeX
|
||||
cmp #$ff
|
||||
bne overCheckY1
|
||||
lda #39
|
||||
sta snakeX
|
||||
overCheckY1:
|
||||
lda snakeY
|
||||
cmp #25
|
||||
bne overCheckY0
|
||||
lda #1
|
||||
sta snakeY
|
||||
overCheckY0
|
||||
lda snakeY
|
||||
cmp #0
|
||||
bne overEndCheck
|
||||
lda #24
|
||||
sta snakeY
|
||||
overEndCheck:
|
||||
|
||||
; Put new head coordinates in list
|
||||
ldy listStart
|
||||
lda snakeX
|
||||
sta listX,y
|
||||
lda snakeY
|
||||
sta listY,y
|
||||
iny
|
||||
sty listStart
|
||||
|
||||
ldy #0
|
||||
|
||||
; Check for food eat / wall hit / self-eat
|
||||
; - - - - - - - - - - - - - - - - - - - - - -
|
||||
; --- Food eat ---
|
||||
lda snakeX ; calc head location in memory
|
||||
sta calcTileX
|
||||
lda snakeY
|
||||
sta calcTileY
|
||||
jsr calcTileMem
|
||||
lda (tileMem),y ; read content of head memory location
|
||||
cmp #FOOD_TILE
|
||||
beq foodEaten ; if memory does contain food, then perform foodEaten actions,
|
||||
jmp checkSelfEat ; else just loooong jump to test if I ate myself
|
||||
foodEaten:
|
||||
ldx length ; else, increment snake length,
|
||||
inx
|
||||
stx length
|
||||
genFood:
|
||||
ldx random
|
||||
inx
|
||||
stx random
|
||||
|
||||
txa
|
||||
genFoodX: ; calculate `random` modulo SCREEN_W
|
||||
sec
|
||||
sbc #SCREEN_W
|
||||
cmp #SCREEN_W
|
||||
bcs genFoodX
|
||||
sta calcTileX
|
||||
|
||||
txa
|
||||
genFoodY: ; calculate `random` modulo 22 (22 = SCREEN_H - 1)
|
||||
sec
|
||||
sbc #22
|
||||
cmp #22
|
||||
bcs genFoodY
|
||||
clc ; add 1 because 1st line can not be used
|
||||
adc #1
|
||||
sta calcTileY
|
||||
|
||||
; Now I have X and Y coordinate for food stored in calcTileX, calcTileY
|
||||
; and I must check it is not the location that I am going to overwrite
|
||||
; with the head in draw snake head...
|
||||
lda calcTileX
|
||||
cmp snakeX
|
||||
bne foodOK
|
||||
lda calcTileY
|
||||
cmp snakeY
|
||||
beq genFood
|
||||
foodOK:
|
||||
; debug -- print choosen X,Y for food
|
||||
; ldy #$18
|
||||
; lda calcTileX
|
||||
; jsr printByte
|
||||
; ldy #$1b
|
||||
; lda calcTileY
|
||||
; jsr printByte
|
||||
|
||||
ldy #0
|
||||
jsr calcTileMem ; calc food address in memory
|
||||
lda (tileMem),y ; check if memory is empty
|
||||
cmp #$20 ; is there a space?
|
||||
bne genFood ; if not, must generate another number
|
||||
lda #FOOD_TILE ; else, just put that fucking piece of food there
|
||||
sta (tileMem),y
|
||||
|
||||
lda #$d4
|
||||
clc
|
||||
adc tileMem + 1
|
||||
sta tileMem + 1
|
||||
lda #FOOD_COLOR
|
||||
sta (tileMem),y
|
||||
|
||||
; print score at $10th column
|
||||
ldy #$10
|
||||
lda length
|
||||
jsr printByte
|
||||
|
||||
jmp checkEndSelfEat
|
||||
checkEndFood:
|
||||
|
||||
; --- Self eat ---
|
||||
checkSelfEat:
|
||||
cmp #SNAKE_TILE
|
||||
bne checkEndSelfEat
|
||||
jmp gameover
|
||||
checkEndSelfEat:
|
||||
|
||||
; Draw snake head
|
||||
ldy #0
|
||||
lda snakeX ; calc char address in video memory, and put SNAKE_TILE
|
||||
sta calcTileX
|
||||
lda snakeY
|
||||
sta calcTileY
|
||||
jsr calcTileMem
|
||||
lda #SNAKE_TILE
|
||||
sta (tileMem),y
|
||||
|
||||
lda #$d4 ; add #$d400 to previous address (obtain color memory
|
||||
clc ; correspondent), and put SNAKE_COLOR
|
||||
adc tileMem + 1
|
||||
sta tileMem + 1
|
||||
lda #SNAKE_COLOR
|
||||
sta (tileMem),y
|
||||
|
||||
; Erase snake tail
|
||||
lda listStart ; take start of list, and subtract snake length,
|
||||
sec ; to obtain index of end of list
|
||||
sbc length
|
||||
tax ; use previous value as index in list, and calc video memory address
|
||||
lda listX,x
|
||||
sta calcTileX
|
||||
lda listY,x
|
||||
sta calcTileY
|
||||
jsr calcTileMem
|
||||
lda #$20 ; just put a space to erase snake tail tile
|
||||
sta (tileMem),y
|
||||
|
||||
skipPauseTests:
|
||||
|
||||
rts
|
||||
|
||||
; Game is over
|
||||
; ----------------------------------------------------------------------
|
||||
gameover:
|
||||
lda #<gameoverString
|
||||
sta printStatusString
|
||||
lda #>gameoverString
|
||||
sta printStatusString + 1
|
||||
jsr printStatus
|
||||
|
||||
; Set gameover and outro status
|
||||
lda #$ff
|
||||
sta outroDelay
|
||||
lda #ST_OUTRO
|
||||
sta status
|
||||
rts
|
||||
|
||||
; Decrement outroDelay, just to let player see her/his end screen
|
||||
; with score
|
||||
statusOutro:
|
||||
ldy outroDelay ; load outroDelay and decrement
|
||||
dey
|
||||
sty outroDelay
|
||||
cpy #0
|
||||
beq statusOutroEnd
|
||||
rts
|
||||
statusOutroEnd:
|
||||
; Set status as ST_END: this way, the loop out of this interrupt,
|
||||
; will know that we finished, and will play the intro again
|
||||
lda #ST_END
|
||||
sta status
|
||||
rts
|
||||
|
||||
; Subroutines
|
||||
; ----------------------------------------------------------------------
|
||||
; Do some math to calculate tile address in video memory
|
||||
; using x,y coordinates
|
||||
; Formula: addr = $400 + y * SCREEN_W + x
|
||||
calcTileMem:
|
||||
; Save registers
|
||||
pha
|
||||
txa
|
||||
pha
|
||||
tya
|
||||
pha
|
||||
|
||||
; Set tileMem to $400
|
||||
lda #$00
|
||||
sta tileMem
|
||||
lda #$04
|
||||
sta tileMem + 1
|
||||
|
||||
ldy calcTileY ; Get head Y coordinate
|
||||
calcTileMult:
|
||||
tya
|
||||
beq calcTileEnd ; if Y is equal to zero, nothing to do, just skip moltiplication, else...
|
||||
dey ; decrement Y
|
||||
clc
|
||||
lda #SCREEN_W ; A = screen width = 40
|
||||
adc tileMem ; A = screen width + tileMem (low)
|
||||
sta tileMem ; update tileMem (low)
|
||||
lda #0 ; do the same with higher byte: A = 0
|
||||
adc tileMem + 1 ; add (eventual) carry
|
||||
sta tileMem + 1 ; update tileMem (high)
|
||||
jmp calcTileMult ; do again until Y == 0
|
||||
calcTileEnd: ; now multiplication is ended, so add X
|
||||
lda calcTileX
|
||||
adc tileMem
|
||||
sta tileMem
|
||||
lda #0
|
||||
adc tileMem + 1
|
||||
sta tileMem + 1
|
||||
|
||||
; Restore old registers
|
||||
pla
|
||||
tay
|
||||
pla
|
||||
tax
|
||||
pla
|
||||
|
||||
rts
|
||||
|
||||
; Print a byte in hexadecimal
|
||||
; A input register for byte to print
|
||||
; Y input register for printing colum (on first line)
|
||||
printByte:
|
||||
; Copy parameter also in X
|
||||
tax
|
||||
|
||||
lsr ; Take most significant nibble
|
||||
lsr
|
||||
lsr
|
||||
lsr
|
||||
jsr printDigit
|
||||
sta $400,y ; print msb char
|
||||
|
||||
txa ; Take least significant nibble (use previous copy)
|
||||
and #$0f
|
||||
jsr printDigit
|
||||
sta $401,y ; print lsb char
|
||||
|
||||
rts
|
||||
|
||||
; Transform a base-36 digit into a Commodore screen code
|
||||
; Leave input digit in accumulator; returns output screen code in accumulator
|
||||
printDigit:
|
||||
cmp #10
|
||||
bcs printDigitL ; if it is not a decimal digit, then go to printDigitL
|
||||
clc ; it is a decimal digit! Just add `0` (48)
|
||||
adc #48
|
||||
ora #$80 ; reverse color
|
||||
rts
|
||||
printDigitL: ; it is not a decimal digit, then...
|
||||
sec
|
||||
sbc #10 ; take away 10
|
||||
clc
|
||||
adc #1 ; add 1, so you obtain something in [A-F]
|
||||
ora #$80 ; reverse color
|
||||
rts
|
||||
|
||||
; Print null-terminated string on status bar
|
||||
; address of string is given in input using memory location printStatusString
|
||||
printStatus:
|
||||
ldy #0
|
||||
printStatusLoop:
|
||||
lda (printStatusString),y
|
||||
beq printStatusEnd
|
||||
cmp #$20
|
||||
bne printStatusSkipSpace
|
||||
lda #$60
|
||||
printStatusSkipSpace:
|
||||
sec
|
||||
sbc #$40 ; convert from standard ASCII to Commodore screen code
|
||||
ora #$80 ; reverse color
|
||||
sta $413,y
|
||||
iny
|
||||
jmp printStatusLoop
|
||||
printStatusEnd:
|
||||
rts
|
||||
|
||||
; Print string for intro
|
||||
; Input parameters:
|
||||
; printIntroString pointer to string to be printed (source)
|
||||
; introScreenStart pointer to text video memory on screen where to print (dest)
|
||||
printIntro:
|
||||
ldy #0
|
||||
printIntroLoop:
|
||||
lda (printIntroString),y ; get char from string
|
||||
beq printIntroEnd ; if zero, then end (string must be null-terminated)
|
||||
cmp #$40 ; is char greater or equal to #$40 = #64 = `@' ?
|
||||
bcc printIntroEndCheck ; if not, it is less, thus it must be
|
||||
; a full stop, comma, colon or something
|
||||
; that actually has the same value in both
|
||||
; true ASCII and in PET screen codes
|
||||
; otherwise, it is greater than `@`, so must
|
||||
; subtract 64 because CBM and its encodings
|
||||
; are simply a big shit
|
||||
sec
|
||||
sbc #$40
|
||||
|
||||
printIntroEndCheck:
|
||||
sta (introScreenStart),y ; put screen code to screen
|
||||
iny ; next char in string
|
||||
jmp printIntroLoop
|
||||
printIntroEnd:
|
||||
rts
|
||||
|
||||
; Include
|
||||
; ______________________________________________________________________
|
||||
INCLUDE "multicolor.asm"
|
||||
|
||||
#if DEBUG = 1
|
||||
ECHO "Program ends at: ",.
|
||||
#endif
|
||||
;
|
||||
; coded during december 2017
|
||||
; by giomba -- giomba at glgprograms.it
|
||||
; this software is free software and is distributed
|
||||
; under the terms of GNU GPL v3 license
|
||||
;
|
||||
|
||||
; vim: set expandtab tabstop=4 shiftwidth=4:
|
||||
135
subroutines.asm
Normal file
135
subroutines.asm
Normal file
@ -0,0 +1,135 @@
|
||||
; Subroutines
|
||||
; ----------------------------------------------------------------------
|
||||
; Do some math to calculate tile address in video memory
|
||||
; using x,y coordinates
|
||||
; Formula: addr = $400 + y * SCREEN_W + x
|
||||
calcTileMem:
|
||||
; Save registers
|
||||
pha
|
||||
txa
|
||||
pha
|
||||
tya
|
||||
pha
|
||||
|
||||
; Set tileMem to $400
|
||||
lda #$00
|
||||
sta tileMem
|
||||
lda #$04
|
||||
sta tileMem + 1
|
||||
|
||||
ldy calcTileY ; Get head Y coordinate
|
||||
calcTileMult:
|
||||
tya
|
||||
beq calcTileEnd ; if Y is equal to zero, nothing to do, just skip moltiplication, else...
|
||||
dey ; decrement Y
|
||||
clc
|
||||
lda #SCREEN_W ; A = screen width = 40
|
||||
adc tileMem ; A = screen width + tileMem (low)
|
||||
sta tileMem ; update tileMem (low)
|
||||
lda #0 ; do the same with higher byte: A = 0
|
||||
adc tileMem + 1 ; add (eventual) carry
|
||||
sta tileMem + 1 ; update tileMem (high)
|
||||
jmp calcTileMult ; do again until Y == 0
|
||||
calcTileEnd: ; now multiplication is ended, so add X
|
||||
lda calcTileX
|
||||
adc tileMem
|
||||
sta tileMem
|
||||
lda #0
|
||||
adc tileMem + 1
|
||||
sta tileMem + 1
|
||||
|
||||
; Restore old registers
|
||||
pla
|
||||
tay
|
||||
pla
|
||||
tax
|
||||
pla
|
||||
|
||||
rts
|
||||
|
||||
; Print a byte in hexadecimal
|
||||
; A input register for byte to print
|
||||
; Y input register for printing colum (on first line)
|
||||
printByte:
|
||||
; Copy parameter also in X
|
||||
tax
|
||||
|
||||
lsr ; Take most significant nibble
|
||||
lsr
|
||||
lsr
|
||||
lsr
|
||||
jsr printDigit
|
||||
sta $400,y ; print msb char
|
||||
|
||||
txa ; Take least significant nibble (use previous copy)
|
||||
and #$0f
|
||||
jsr printDigit
|
||||
sta $401,y ; print lsb char
|
||||
|
||||
rts
|
||||
|
||||
; Transform a base-36 digit into a Commodore screen code
|
||||
; Leave input digit in accumulator; returns output screen code in accumulator
|
||||
printDigit:
|
||||
cmp #10
|
||||
bcs printDigitL ; if it is not a decimal digit, then go to printDigitL
|
||||
clc ; it is a decimal digit! Just add `0` (48)
|
||||
adc #48
|
||||
ora #$80 ; reverse color
|
||||
rts
|
||||
printDigitL: ; it is not a decimal digit, then...
|
||||
sec
|
||||
sbc #10 ; take away 10
|
||||
clc
|
||||
adc #1 ; add 1, so you obtain something in [A-F]
|
||||
ora #$80 ; reverse color
|
||||
rts
|
||||
|
||||
; Print null-terminated string on status bar
|
||||
; address of string is given in input using memory location printStatusString
|
||||
printStatus:
|
||||
ldy #0
|
||||
printStatusLoop:
|
||||
lda (printStatusString),y
|
||||
beq printStatusEnd
|
||||
cmp #$20
|
||||
bne printStatusSkipSpace
|
||||
lda #$60
|
||||
printStatusSkipSpace:
|
||||
sec
|
||||
sbc #$40 ; convert from standard ASCII to Commodore screen code
|
||||
ora #$80 ; reverse color
|
||||
sta $413,y
|
||||
iny
|
||||
jmp printStatusLoop
|
||||
printStatusEnd:
|
||||
rts
|
||||
|
||||
; Print string for intro
|
||||
; Input parameters:
|
||||
; printIntroString pointer to string to be printed (source)
|
||||
; introScreenStart pointer to text video memory on screen where to print (dest)
|
||||
printIntro:
|
||||
ldy #0
|
||||
printIntroLoop:
|
||||
lda (printIntroString),y ; get char from string
|
||||
beq printIntroEnd ; if zero, then end (string must be null-terminated)
|
||||
cmp #$40 ; is char greater or equal to #$40 = #64 = `@' ?
|
||||
bcc printIntroEndCheck ; if not, it is less, thus it must be
|
||||
; a full stop, comma, colon or something
|
||||
; that actually has the same value in both
|
||||
; true ASCII and in PET screen codes
|
||||
; otherwise, it is greater than `@`, so must
|
||||
; subtract 64 because CBM and its encodings
|
||||
; are simply a big shit
|
||||
sec
|
||||
sbc #$40
|
||||
|
||||
printIntroEndCheck:
|
||||
sta (introScreenStart),y ; put screen code to screen
|
||||
iny ; next char in string
|
||||
jmp printIntroLoop
|
||||
printIntroEnd:
|
||||
rts
|
||||
|
||||
|
||||
20
zeropage.asm
Normal file
20
zeropage.asm
Normal file
@ -0,0 +1,20 @@
|
||||
; Zero page utilities
|
||||
; ----------------------------------------------------------------------
|
||||
; Where is the snake head in video memory? Do math to calculate address
|
||||
; using pointer at tileMem,tileMem+1
|
||||
tileMem DS 2
|
||||
|
||||
; Pointer to status string
|
||||
printStatusString DS 2
|
||||
|
||||
; Pointer to intro string
|
||||
printIntroString DS 2
|
||||
; Pointer to screen position where to print intro string ($fb-$fc)
|
||||
introScreenStart DS 2
|
||||
|
||||
#if DEBUG = 1
|
||||
; Locations $90-$FF in zeropage are used by kernal
|
||||
ECHO "End of zeropage variables. Space left: ",($90 - .)
|
||||
#endif
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user