; DoDraw storage in $91-92
TurtleDraw: ds 1 ; used for drawing player0
BirdDraw: ds 1 ; used for drawing player1
+BallDraw: ds 1
; DoDraw Graphic Pointer in $93-94
TurtlePtr: ds 2 ; used for drawing player0
BirdPtr: ds 2 ; used for drawing player1
+M0Ptr: ds 2
+
+; used for Bird AI to keep track of movement
+BirdAICounter ds 1
+BirdLeftRightStatus ds 1
+BirdUpDownStatus ds 1
; map pointer used for map rendering
MapPtr0: ds 2 ; used for drawing map
PreviousX ds 4
PreviousY ds 4
+; used by Random for an 8 bit random number
+Rand8 ds 1
+
; ---------- Constants
SEG.U constants
; scanlines so actual height is 180 = 90*2
PFHEIGHT = 89 ; 180 scanlines of playfield h
NULL = 0 ; just 0
+P0STARTX = $4D
+P0STARTY = $32
+P1STARTX = 0
+P1STARTY = 0
+BallHeight = 8
;===============================================================================
; Define Start of Cartridge
SEG CODE ; define code segment
; ----------
- ORG $F000 ; 4k carts start at $F000
+ ORG $F800 ; 4k carts start at $F000
Reset
; clear all ram and registers
; Init, run once only!
+ ; seed the random number generator
+ lda INTIM ; unknown value
+ sta Rand8 ; use as seed
+ eor #$FF ; both seed values cannot be 0, so flip the bits
+
; set up srptie pos
ldx #0
; reset lives, map and level to 0
- stx Lives
- stx Level
stx CurrentMap
- ldx #15
- stx ObjectX
- ldx #12
- stx ObjectX+1
- ldy #$30
- sty ObjectY
- sty ObjectY+1
+ ldx #5
+ stx Lives ; 5 lives
+ jsr NextLevel
+
+ jsr ResetPPositions
+
+ jsr SetBallPosition
jsr PlayIntroSong
sta GRP0
sta WSYNC
sta VSYNC
+
+ lda #$30 ;
+ sta NUSIZ0 ; set missile0 to be 8x
+ sta NUSIZ1
Sleep12 ; jsr here to sleep for 12 cycles
rts
; restore y
ldy Temp+1
+ ; ball stuff
+ ldx #1 ; d1=0 so ball will be off
+ lda #BallHeight-1 ; height of ball gfx
+ dcp BallDraw ; decrement and compare
+ bcs DoEnableBall
+ .byte $24
+DoEnableBall
+ inx ; d1=1 so ball will be on
+
; precalculate date for next line
lda #TURTLEHEIGHT-1 ; height of gfx
dcp BirdDraw ; decrement BirdDraw
sta WSYNC
; start of line 2 of the 2LK
sta GRP1
-
+ stx ENABL ; enable ball
dey ; decrease the loop counter
bne pfLoop ; branch if more left to draw
Player2UpNotPressed
rts
+; this sub handles the bird AI
BirdAI
+ ldx #0
+ cpx BirdAICounter
+ bne MoveBirdAI ; jump to keep doing what we are doing
+ ; first we call Random to determine which direction bird moves
+ jsr Random
+ ; if random is even move left, else right
+ lda #1 ; bit mask
+ and Rand8
+ beq EvenLeftRightBirdAI; is even
+
+ ; odd bird AI
+ ldx #0
+ stx BirdLeftRightStatus
+ jmp LeftRightBirdAIDone
+ ; even bird AI
+EvenLeftRightBirdAI
+ ldx #1
+ stx BirdLeftRightStatus
+LeftRightBirdAIDone
+
+ jsr Random
+ ; if random is even move up, else down
+ lda #1 ; bit mask
+ and Rand8
+ beq EvenBirdUpDownBirdAI; is even
+
+ ; odd
+ ldx #0
+ stx BirdUpDownStatus
+ jmp UpDownBirdAIDone
+ ; even
+EvenBirdUpDownBirdAI
+ ldx #1
+ stx BirdUpDownStatus
+UpDownBirdAIDone
+ ldx #20 ; bird ai will follow this pattern for 20 frames
+ stx BirdAICounter
+
+MoveBirdAI
+ dec BirdAICounter
+ ; now we check where to move bird
+ ldx #1
+ cpx BirdUpDownStatus
+ beq MoveBirdUp
+
+ ; odd bird AI
+ ldy #1
+ ldx #2
+ jsr MoveObject
+ jmp UpDownBirdMoveDone
+MoveBirdUp
+ ldy #1
+ ldx #3
+ jsr MoveObject
+UpDownBirdMoveDone
+
+ ldx #1
+ cpx BirdLeftRightStatus
+ beq MoveBirdLeft
+ ; move right
+ ldy #1
+ ldx #0
+ jsr MoveObject
+ jmp leftRightBirdMoveDone
+MoveBirdLeft
+ ldy #1
+ ldx #1
+ jsr MoveObject
+leftRightBirdMoveDone
rts
;====================
; 2 = bird collision
; 3 = missile collision
;====================
-MoveObject ; for some reason the first frame of collision does not detect?
+MoveObject
cpx #0
beq RightCollision
cpx #1
bit CXPPMM
bpl NoP0P1Collision
dec Lives ; kill p0
+ lda #0 ; if lives is 0 - reset the game
+ cmp Lives
+ bne NoReset
+ jmp Reset
+NoReset
+ jsr ResetPPositions
NoP0P1Collision ; p0 and p1 did not collide!
+
+ ; now we dio p0 m0 collision. m0 must be collected by turtle to advance
+ ; each time collision happens m0 will get a new position
+ bit CXP0FB
+ bvc NoP0BallCollision
+
+ stx Score
+ cpx Score
+ beq NoP0BallCollision ; prevent underflow!
+ ; dec score. if screen is left and score is 0 continue
+ dec Score
+ jsr SetBallPosition ; new position for m0
+NoP0BallCollision
+ ; now we check if m0 is in a wall
+ bit CXBLPF
+ beq NoBallPFCollision ; if it is reloacte
+ jsr SetBallPosition
+NoBallPFCollision
+ ; now we check if ball is oob
+ ldx ObjectX+2
+ cpx #160
+ bpl BallNotOOB ; if smaller do nothing
+ ldx ObjectY+2
+ cpx 255
+ bpl BallNotOOB
+ jsr SetBallPosition
+BallNotOOB
CollisionDone
lda #1
sta CXCLR ; clear collision
rts
-PlayerCollision
- ; now we do special case collision
- ; first collision between p1 and p0
- ldx Temp ; x must be 1 if p1 and p0 collided
- cpx #1
- bne NoPlayerCollision
-
- ; if player is hit by bird remove a life
- dec Lives
-
-NoPlayerCollision
- rts
-
; Plays the Intro noise
PlayIntroSong
lda #2
sta AUDV0
rts
+SetBallPosition
+ jsr Random
+ ;ldx Rand8
+ ldx #10
+ stx ObjectX+2
+ jsr Random
+ ;ldx Rand8
+ ldx #10
+ stx ObjectY+2
+ rts
+
+ResetPPositions
+ ldx #P0STARTX
+ stx ObjectX
+ ldy #P0STARTY
+ sty ObjectY
+
+ ldx P1STARTX
+ stx ObjectX+1
+ ldx P1STARTY
+ stx ObjectY+1
+ rts
+
+NextLevel
+ inc Level
+ inc Lives
+ lda #3
+ adc Level
+ ; score is 3 + level
+ sta Score
+ rts
+
SetObjectColours
ldx #3 ; we're going to set 4 colours
ldy #3 ;
PrepScoreForDisplay
; for testing purposes, change the values in Timer and Score
- inc Timer ; inc timer by 1
- bne PSFDskip ; branch if not 0
- inc Score ; inc score by 1 if Timer just rolled to 0
+ ; inc Timer ; inc timer by 1
+ ; bne PSFDskip ; branch if not 0
+ ; inc Score ; inc score by 1 if Timer just rolled to 0
+ ldx Lives
+ stx Timer
PSFDskip
ldx #1 ; use x as the loop counter for PSFDloop
PSFDloop
rts
PositionObjects
- ldx #1 ; position objects 0-1: player0 and player1
+ ldx #3 ; position objects 0-1: player0 and player1 and m0
POloop
lda ObjectX,x ; get the object's X position
jsr PosObject ; set coarse X position and fine-tune amount
lda #0
sta AnimationTimer+1
+ ; prep balls y position
+ ldx #1 ; preload X for setting VDELBL
+ lda ObjectY+2 ; get the balls's Y position
+ clc
+ adc #1 ; add 1 to compensate for priming of ball
+ lsr ; divide by 2 for the 2LK position
+ sta Temp ; save for position calculations
+ bcs NoDelayBL ; if carry is set we don't need Vertical Delay
+ stx VDELBL ; carry was clear, so set Vertical Delay
+
+NoDelayBL
+ lda #(PFHEIGHT + BallHeight + 1)
+ sec
+ sbc Temp
+ sta BallDraw
RenderDone
; use Difficulty Switches to test how Vertical Delay works
- ldx #0
- stx VDELP0 ; turn off VDEL for player0
- stx VDELP1 ; turn off VDEL for player1
- inx
- bit SWCHB ; state of Right Difficult in N (negative flag)
+ ;ldx #0
+ ;stx VDELP0 ; turn off VDEL for player0
+ ;stx VDELP1 ; turn off VDEL for player1
+ ;inx
+ ;bit SWCHB ; state of Right Difficult in N (negative flag)
; state of Left Difficult in V (overflow flag)
- bvc LeftIsB
- stx VDELP0 ; Left is A, turn on VDEL for player0
-LeftIsB
- bpl RightIsB
- stx VDELP1 ; Right is A, turn on VDEL for player1
-RightIsB
+ ;bvc LeftIsB
+ ;stx VDELP0 ; Left is A, turn on VDEL for player0
+;LeftIsB
+ ;bpl RightIsB
+ ;stx VDELP1 ; Right is A, turn on VDEL for player1
+;RightIsB
rts
;===============================================================================
sta RESP0,X ; 4 23 - set coarse X position of object
rts ; 6 29
+;===============================================================================
+; This routine returns a random number based on the last value of Rand8
+; Expected inputs:
+; none
+; Returns: A 8-bit random number in Rand8
+;===============================================================================
+Random
+ lda Rand8
+ lsr
+ bcc noeor
+ eor #$B4
+noeor
+ sta Rand8
+ rts
+
+#if SYSTEM = NTSC
Colours:
.byte $C6 ; green - goes into COLUP0, color for player1 and missile0
.byte $86 ; blue - goes into COLUP1, color for player0 and missile1
.byte $06 ; dark grey - goes into COLUP1, B&W for player1 and missile1
.byte $0A ; light grey - goes into COLUPF, B&W for playfield and ball
.byte $00 ; black - goes into COLUBK, B&W for background
+#endif
+
+#if SYSTEM = PAL
+Colours:
+ .byte $3A ; green - goes into COLUP0, color for player1 and missile0
+ .byte $B4 ; blue - goes into COLUP1, color for player0 and missile1
+ .byte $66 ; red - goes into COLUPF, color for playfield and ball
+ .byte $00 ; black - goes into COLUBK, color for background
+ .byte $0E ; white - goes into COLUP0, B&W for player0 and missile0
+ .byte $14 ; dark grey - goes into COLUP1, B&W for player1 and missile1
+ .byte $1A ; light grey - goes into COLUPF, B&W for playfield and ball
+ .byte $00 ; black - goes into COLUBK, B&W for background
+#endif
; Sprite data
TurtleSprite:
projects / turtlebay / .git / commitdiff