Game 1 Unit 15 of 64 1 hr learning time
Game States
Title screen. Playing. Game over. Complete game flow.
23% of Signal
What You’re Building
Game flow.
A game isn’t complete without proper presentation. Players need a title screen to start, gameplay to enjoy, and a game over screen to reflect on their performance. This unit adds a state machine that manages these three states.
By the end of this unit:
- Title screen with “SIGNAL”
- Press fire to start
- Gameplay until game over
- Game over screen with score
- Press fire to return to title
The State Machine
We add a high-level game_state variable to control which screen is active:
; Game state constants (high-level game flow)
; These control which screen is active, separate from frog_state
GSTATE_TITLE equ 0 ; Title screen, waiting for fire
GSTATE_PLAYING equ 1 ; Active gameplay
GSTATE_OVER equ 2 ; Game over screen
; Title screen position
TITLE_Y equ 100 ; Vertical position for "SIGNAL" text
; Variables
game_state: dc.w 0 ; High-level game state (title/playing/over)
fire_prev: dc.w 0 ; Previous fire button state for edge detection
This is separate from frog_state (IDLE, HOPPING, DYING, GAMEOVER) which tracks the frog’s animation state during gameplay.
Main Loop Dispatch
The main loop now dispatches based on game_state:
;==============================================================================
; MAIN LOOP - Dispatches based on game_state
;==============================================================================
mainloop:
bsr wait_vblank
move.w game_state,d0
cmp.w #GSTATE_TITLE,d0
beq title_loop
cmp.w #GSTATE_OVER,d0
beq gameover_loop
; GSTATE_PLAYING - active gameplay
bsr update_frog
bsr update_sprite
; Check if frog died (transition to game over)
cmp.w #STATE_GAMEOVER,frog_state
beq .enter_gameover
; ... rest of game logic ...
bra mainloop
.enter_gameover:
move.w #GSTATE_OVER,game_state
bsr show_gameover
bra mainloop
Each state has its own handler. The playing state runs the full game update. Title and game over states just wait for fire button input.
Fire Button Edge Detection
We need edge detection to prevent a single press from triggering multiple transitions:
;------------------------------------------------------------------------------
; READ_FIRE_EDGE - Detect fire button press (edge triggered)
; Returns: D0 = 1 if fire just pressed, 0 otherwise
;
; Edge detection prevents a held button from triggering multiple times.
; We only return true on the frame when the button transitions from
; not-pressed to pressed.
;------------------------------------------------------------------------------
read_fire_edge:
btst #7,$bfe001 ; Fire button (active low)
seq d0 ; D0 = $FF if pressed, $00 if not
and.w #1,d0 ; D0 = 1 if pressed
move.w fire_prev,d1
move.w d0,fire_prev
not.w d1 ; D1 = 1 if was NOT pressed
and.w d1,d0 ; D0 = 1 only on rising edge
rts
; The SEQ instruction sets the destination to $FF if the Z flag is set.
; Since BTST clears Z when the tested bit is 0 (button pressed = active low),
; SEQ gives us $FF when pressed, $00 when not pressed.
The seq instruction sets d0 to $FF if the zero flag is set (button pressed since btst clears Z for bit=0). We compare current state with previous state to detect the moment of pressing.
Title Screen
The title screen displays “SIGNAL” and waits for fire:
;------------------------------------------------------------------------------
; TITLE_LOOP - Wait for fire button on title screen
;------------------------------------------------------------------------------
title_loop:
bsr read_fire_edge
tst.w d0
beq mainloop ; No fire press, keep waiting
; Fire pressed - start game!
move.w #GSTATE_PLAYING,game_state
bsr init_game
bsr clear_screen
bsr update_life_display
bsr display_score
bsr display_timer
bsr display_level
bsr update_sprite
bra mainloop
;------------------------------------------------------------------------------
; GAMEOVER_LOOP - Wait for fire button on game over screen
;------------------------------------------------------------------------------
gameover_loop:
bsr read_fire_edge
tst.w d0
beq mainloop ; No fire press, keep waiting
; Fire pressed - return to title
move.w #GSTATE_TITLE,game_state
bsr clear_screen
bsr show_title
bra mainloop
We hide the frog sprite during the title by clearing its control words:
;------------------------------------------------------------------------------
; SHOW_TITLE - Display title screen
;------------------------------------------------------------------------------
show_title:
bsr clear_screen
bsr wait_blit
; Hide frog sprite during title
lea frog_data,a0
clr.l (a0)
; Hide life sprites
lea life_icon_1,a0
clr.l (a0)
lea life_icon_2,a0
clr.l (a0)
lea life_icon_3,a0
clr.l (a0)
; Draw "SIGNAL" text centred on screen
; Each letter is 8 pixels wide, "SIGNAL" = 6 letters = 48 pixels
; Centre: (320-48)/2 = 136 pixels = 17 bytes
lea screen_plane,a2
add.l #TITLE_Y*SCREEN_W+17,a2
lea title_text,a1
moveq #5,d4 ; 6 letters
.draw_letter:
move.w (a1)+,d0 ; Get letter index
lsl.w #4,d0 ; *16 for font offset
lea letter_font,a0
add.w d0,a0
move.l a2,a3
moveq #7,d3
.copy_row:
move.b (a0),(a3)
addq.l #2,a0
lea SCREEN_W(a3),a3
dbf d3,.copy_row
addq.l #1,a2
dbf d4,.draw_letter
rts
Letter Font
We extend our digit font with letters needed for “SIGNAL” and “GAME OVER”:
; Letter font for title/game over text
; Letters indexed: A=0, E=1, G=2, I=3, L=4, M=5, N=6, O=7, R=8, S=9, V=10
; Same 8x8 format as digit font (16 bytes per glyph)
even
letter_font:
; A (index 0)
dc.w $3c00 ; ..XXXX..
dc.w $6600 ; .XX..XX.
dc.w $6600 ; .XX..XX.
dc.w $7e00 ; .XXXXXX.
dc.w $6600 ; .XX..XX.
dc.w $6600 ; .XX..XX.
dc.w $6600 ; .XX..XX.
dc.w $0000 ; ........
; E (index 1)
dc.w $7e00 ; .XXXXXX.
dc.w $6000 ; .XX.....
dc.w $6000 ; .XX.....
dc.w $7c00 ; .XXXXX..
dc.w $6000 ; .XX.....
dc.w $6000 ; .XX.....
dc.w $7e00 ; .XXXXXX.
dc.w $0000 ; ........
; ... (more letters follow same pattern)
; Text data - "SIGNAL" as indices into letter_font
title_text:
dc.w 9,3,2,6,0,4 ; S=9, I=3, G=2, N=6, A=0, L=4
; Text data - "GAME OVER" (99 = space character)
gameover_text:
dc.w 2,0,5,1,99,7,10,1,8 ; G A M E _ O V E R
Each letter is stored as 8 rows of 16-bit words (same format as digit font). The text data is an array of indices into the font.
Game Over Screen
When the player loses their last life, we transition to game over:
.enter_gameover:
move.w #GSTATE_OVER,game_state
bsr show_gameover
bra mainloopThe game over screen overlays “GAME OVER” on the frozen gameplay, letting players see their final score:
show_gameover:
; Draw "GAME OVER" text over the game screen
lea screen_plane,a2
add.l #120*SCREEN_W+15,a2
lea gameover_text,a1
; ... draw each letterState Transitions
The complete flow:
- Start: Game begins in GSTATE_TITLE
- Title → Playing: Fire button triggers init_game
- Playing → Game Over: Last life lost (frog_state = STATE_GAMEOVER)
- Game Over → Title: Fire button returns to title
┌─────────┐ fire ┌─────────┐
│ TITLE │───────────────►│ PLAYING │
└─────────┘ └────┬────┘
▲ │
│ fire │ no lives
│ ┌──────────┐ │
└──────│GAME OVER │◄────────┘
└──────────┘Initialisation Changes
The startup code now shows the title screen instead of jumping straight into gameplay:
; Start at title screen
move.w #GSTATE_TITLE,game_state
bsr show_titleThe game only initialises when the player presses fire on the title screen.
Key Takeaways
- State machine separates game flow from game logic
- High-level states (title/playing/over) vs animation states (idle/hopping/dying)
- Edge detection prevents button bouncing
- Font extension reuses digit rendering for letters
- Overlay text keeps final score visible on game over
- Clean transitions between all states
The Code
;==============================================================================
; SIGNAL - A Frogger-style game for the Commodore Amiga
; Unit 15: Game States
;
; A complete game needs proper flow: title screen, gameplay, game over.
; This unit adds a state machine that manages these transitions.
;==============================================================================
;==============================================================================
; CONSTANTS
;==============================================================================
SCREEN_W equ 40
SCREEN_H equ 256
PLANE_SIZE equ SCREEN_W*SCREEN_H
GRID_COLS equ 20
GRID_ROWS equ 13
CELL_SIZE equ 16
GRID_ORIGIN_X equ 48
GRID_ORIGIN_Y equ 44
START_GRID_X equ 9
START_GRID_Y equ 12
HOP_FRAMES equ 8
PIXELS_PER_FRAME equ 2
STATE_IDLE equ 0
STATE_HOPPING equ 1
STATE_DYING equ 2
STATE_GAMEOVER equ 3
DIR_UP equ 0
DIR_DOWN equ 1
DIR_LEFT equ 2
DIR_RIGHT equ 3
FROG_HEIGHT equ 16
FROG_WIDTH equ 16
DEATH_FRAMES equ 30
FLASH_COLOUR equ $0f00
NUM_CARS equ 10
CAR_WIDTH equ 2
CAR_WIDTH_PX equ 32
CAR_HEIGHT equ 12
CAR_STRUCT_SIZE equ 8
ROAD_ROW_FIRST equ 7
ROAD_ROW_LAST equ 11
START_LIVES equ 3
NUM_HOMES equ 5
HOME_ROW equ 0
POINTS_PER_HOME equ 50
HOME_0_X equ 2
HOME_1_X equ 6
HOME_2_X equ 10
HOME_3_X equ 14
HOME_4_X equ 18
; Score display - position in start zone (below cars)
SCORE_X equ 256 ; Pixel X position (must be byte-aligned)
SCORE_Y equ 236 ; Pixel Y position (grid row 12, in start zone)
DIGIT_H equ 8 ; 8 pixels tall
NUM_DIGITS equ 6 ; Display 6 digits (up to 999,999)
; Timer constants
TIMER_START equ 3000 ; 60 seconds at 50Hz PAL (60 * 50)
TIMER_X equ 56 ; Pixel X position for timer (left side)
TIMER_Y equ 236 ; Same row as score
TIMER_DIGITS equ 2 ; Display 2 digits (00-60)
; Level constants
MAX_LEVEL equ 8 ; Maximum level (endless after this)
LEVEL_X equ 152 ; Pixel X position for level display (centre)
LEVEL_Y equ 236 ; Same row as score/timer
LEVEL_BONUS equ 100 ; Bonus points per level complete
; Game state constants (high-level game flow)
GSTATE_TITLE equ 0 ; Title screen, waiting for fire
GSTATE_PLAYING equ 1 ; Active gameplay
GSTATE_OVER equ 2 ; Game over screen
; Title screen position
TITLE_Y equ 100 ; Vertical position for "SIGNAL" text
; Audio constants
SND_HOP equ 0
SND_DEATH equ 1
SND_HOME equ 2
; Colours
COLOUR_BLACK equ $0000
COLOUR_HOME equ $0282
COLOUR_HOME_LIT equ $03a3
COLOUR_HOME_FILLED equ $0f80
COLOUR_WATER1 equ $0148
COLOUR_WATER2 equ $026a
COLOUR_MEDIAN equ $0383
COLOUR_ROAD1 equ $0333
COLOUR_ROAD2 equ $0444
COLOUR_START equ $0262
COLOUR_START_LIT equ $0373
COLOUR_FROG equ $00f0
COLOUR_EYES equ $0ff0
COLOUR_OUTLINE equ $0000
COLOUR_CAR equ $0f00
;==============================================================================
; HARDWARE REGISTERS
;==============================================================================
CUSTOM equ $dff000
DMACONR equ $002
VPOSR equ $004
JOY1DAT equ $00c
BLTCON0 equ $040
BLTCON1 equ $042
BLTAFWM equ $044
BLTALWM equ $046
BLTCPTH equ $048
BLTBPTH equ $04c
BLTAPTH equ $050
BLTDPTH equ $054
BLTSIZE equ $058
BLTCMOD equ $060
BLTBMOD equ $062
BLTAMOD equ $064
BLTDMOD equ $066
BLTADAT equ $074
COP1LC equ $080
COPJMP1 equ $088
DMACON equ $096
INTENA equ $09a
INTREQ equ $09c
COLOR00 equ $180
SPR0PTH equ $120
SPR0PTL equ $122
SPR1PTH equ $124
SPR1PTL equ $126
SPR2PTH equ $128
SPR2PTL equ $12a
AUD0LC equ $0a0
AUD0LEN equ $0a4
AUD0PER equ $0a6
AUD0VOL equ $0a8
;==============================================================================
; CODE SECTION
;==============================================================================
section code,code_c
start:
lea CUSTOM,a5
move.w #$7fff,INTENA(a5)
move.w #$7fff,INTREQ(a5)
move.w #$7fff,DMACON(a5)
; Enable Blitter DMA for screen clearing and drawing
move.w #$8040,DMACON(a5) ; BLTDMA on
bsr clear_screen
; Set up bitplane pointer
lea screen_plane,a0
move.l a0,d0
swap d0
lea bplpth_val,a1
move.w d0,(a1)
swap d0
lea bplptl_val,a1
move.w d0,(a1)
; Initialise game
bsr init_game
; Set main sprite pointer
lea frog_data,a0
move.l a0,d0
swap d0
lea sprpth_val,a1
move.w d0,(a1)
swap d0
lea sprptl_val,a1
move.w d0,(a1)
bsr setup_life_sprites
bsr update_sprite
bsr update_life_display
; Install copper list
lea copperlist,a0
move.l a0,COP1LC(a5)
move.w d0,COPJMP1(a5)
move.w #$87e1,DMACON(a5)
; Start at title screen
move.w #GSTATE_TITLE,game_state
bsr show_title
;==============================================================================
; MAIN LOOP - Dispatches based on game_state
;==============================================================================
mainloop:
bsr wait_vblank
move.w game_state,d0
cmp.w #GSTATE_TITLE,d0
beq title_loop
cmp.w #GSTATE_OVER,d0
beq gameover_loop
; GSTATE_PLAYING - active gameplay
bsr update_frog
bsr update_sprite
; Check if frog died (transition to game over)
cmp.w #STATE_GAMEOVER,frog_state
beq .enter_gameover
; Update timer (only when not dying)
cmp.w #STATE_DYING,frog_state
beq.s .skip_timer
bsr update_timer
.skip_timer:
bsr erase_all_cars
bsr move_all_cars
bsr draw_all_cars
cmp.w #STATE_DYING,frog_state
beq.s .skip_collision
cmp.w #STATE_IDLE,frog_state
bne.s .skip_collision
bsr check_home
bsr check_collision
.skip_collision:
bra mainloop
.enter_gameover:
move.w #GSTATE_OVER,game_state
bsr show_gameover
bra mainloop
;------------------------------------------------------------------------------
; TITLE_LOOP - Wait for fire button on title screen
;------------------------------------------------------------------------------
title_loop:
bsr read_fire_edge
tst.w d0
beq mainloop ; No fire press, keep waiting
; Fire pressed - start game!
move.w #GSTATE_PLAYING,game_state
bsr init_game
bsr clear_screen
bsr update_life_display
bsr display_score
bsr display_timer
bsr display_level
bsr update_sprite
bra mainloop
;------------------------------------------------------------------------------
; GAMEOVER_LOOP - Wait for fire button on game over screen
;------------------------------------------------------------------------------
gameover_loop:
bsr read_fire_edge
tst.w d0
beq mainloop ; No fire press, keep waiting
; Fire pressed - return to title
move.w #GSTATE_TITLE,game_state
bsr clear_screen
bsr show_title
bra mainloop
;------------------------------------------------------------------------------
; READ_FIRE_EDGE - Detect fire button press (edge triggered)
; Returns: D0 = 1 if fire just pressed, 0 otherwise
;------------------------------------------------------------------------------
read_fire_edge:
btst #7,$bfe001 ; Fire button (active low)
seq d0 ; D0 = $FF if pressed, $00 if not
and.w #1,d0 ; D0 = 1 if pressed
move.w fire_prev,d1
move.w d0,fire_prev
not.w d1 ; D1 = 1 if was NOT pressed
and.w d1,d0 ; D0 = 1 only on rising edge
rts
;------------------------------------------------------------------------------
; SHOW_TITLE - Display title screen
;------------------------------------------------------------------------------
show_title:
bsr clear_screen
bsr wait_blit
; Hide frog sprite during title
lea frog_data,a0
clr.l (a0)
; Hide life sprites
lea life_icon_1,a0
clr.l (a0)
lea life_icon_2,a0
clr.l (a0)
lea life_icon_3,a0
clr.l (a0)
; Draw "SIGNAL" text centred on screen
; Each letter is 8 pixels wide, "SIGNAL" = 6 letters = 48 pixels
; Centre: (320-48)/2 = 136 pixels = 17 bytes
lea screen_plane,a2
add.l #TITLE_Y*SCREEN_W+17,a2
lea title_text,a1
moveq #5,d4 ; 6 letters
.draw_letter:
move.w (a1)+,d0 ; Get letter index
lsl.w #4,d0 ; *16 for font offset
lea letter_font,a0
add.w d0,a0
move.l a2,a3
moveq #7,d3
.copy_row:
move.b (a0),(a3)
addq.l #2,a0
lea SCREEN_W(a3),a3
dbf d3,.copy_row
addq.l #1,a2
dbf d4,.draw_letter
rts
;------------------------------------------------------------------------------
; SHOW_GAMEOVER - Display game over screen with final score
;------------------------------------------------------------------------------
show_gameover:
; Keep the game screen visible but draw "GAME OVER" text
; Draw at centre of screen
lea screen_plane,a2
add.l #120*SCREEN_W+15,a2 ; Centre "GAME OVER" (9 chars = 72px)
lea gameover_text,a1
moveq #8,d4 ; 9 characters (including space)
.draw_letter:
move.w (a1)+,d0
cmp.w #99,d0 ; 99 = space
beq.s .space
lsl.w #4,d0
lea letter_font,a0
add.w d0,a0
move.l a2,a3
moveq #7,d3
.copy_row:
move.b (a0),(a3)
addq.l #2,a0
lea SCREEN_W(a3),a3
dbf d3,.copy_row
.space:
; Space or after drawing - advance to next position
addq.l #1,a2
dbf d4,.draw_letter
rts
;==============================================================================
; SCORE DISPLAY
;==============================================================================
;------------------------------------------------------------------------------
; DISPLAY_SCORE - Convert score to digits and display
; Simplified: just draws "000000" for now
;------------------------------------------------------------------------------
display_score:
movem.l d0-d4/a0-a3,-(sp)
; Convert score to 6 decimal digits
move.l score(pc),d0 ; Use PC-relative addressing
lea score_digits+12,a0 ; Point past end of buffer
moveq #5,d4
.convert:
divu #10,d0 ; d0 low = quotient, d0 high = remainder
swap d0
move.w d0,-(a0) ; Store remainder
clr.w d0
swap d0
dbf d4,.convert
; Draw 6 digits using CPU byte copies (tight 8-pixel spacing)
lea score_digits,a1 ; Digit values
lea screen_plane,a2
add.l #SCORE_Y*SCREEN_W+SCORE_X/8,a2 ; Base destination
moveq #5,d4 ; 6 digits
.draw_digit:
move.w (a1)+,d0 ; Get digit value (0-9)
lsl.w #4,d0 ; *16: each digit = 16 bytes
lea digit_font,a0
add.w d0,a0 ; Point to correct digit
; Copy 8 rows, 1 byte each (CPU, no alignment issues)
move.l a2,a3 ; Dest for this digit
moveq #7,d3 ; 8 rows
.copy_row:
move.b (a0),(a3) ; Copy high byte of word
addq.l #2,a0 ; Next source word
lea SCREEN_W(a3),a3 ; Next dest row
dbf d3,.copy_row
addq.l #1,a2 ; Move right by 1 byte (8 pixels)
dbf d4,.draw_digit
movem.l (sp)+,d0-d4/a0-a3
rts
;==============================================================================
; TIMER ROUTINES
;==============================================================================
;------------------------------------------------------------------------------
; UPDATE_TIMER - Decrement timer and check for timeout
;------------------------------------------------------------------------------
update_timer:
subq.w #1,timer
bgt.s .not_timeout
; Timer reached zero - death!
bsr trigger_death
rts
.not_timeout:
; Display timer every frame
bsr display_timer
rts
;------------------------------------------------------------------------------
; DISPLAY_TIMER - Show remaining seconds on screen
;------------------------------------------------------------------------------
display_timer:
movem.l d0-d4/a0-a3,-(sp)
; Convert timer frames to seconds (timer / 50)
move.w timer(pc),d0
ext.l d0
divu #50,d0 ; d0 = seconds remaining
; Convert to 2 decimal digits
lea timer_digits+4,a0 ; Point past end of buffer
moveq #1,d4 ; 2 digits
.convert:
divu #10,d0
swap d0
move.w d0,-(a0)
clr.w d0
swap d0
dbf d4,.convert
; Draw 2 digits using CPU byte copies
lea timer_digits,a1
lea screen_plane,a2
add.l #TIMER_Y*SCREEN_W+TIMER_X/8,a2
moveq #1,d4 ; 2 digits
.draw_digit:
move.w (a1)+,d0
lsl.w #4,d0 ; *16 for font offset
lea digit_font,a0
add.w d0,a0
move.l a2,a3
moveq #7,d3 ; 8 rows
.copy_row:
move.b (a0),(a3)
addq.l #2,a0
lea SCREEN_W(a3),a3
dbf d3,.copy_row
addq.l #1,a2 ; Next digit position
dbf d4,.draw_digit
movem.l (sp)+,d0-d4/a0-a3
rts
;------------------------------------------------------------------------------
; DISPLAY_LEVEL - Show current level on screen (single digit 1-9)
;------------------------------------------------------------------------------
display_level:
movem.l d0-d4/a0-a3,-(sp)
; Get level (1-9, clamp display to 9)
move.w level(pc),d0
cmp.w #9,d0
ble.s .level_ok
moveq #9,d0 ; Cap display at 9
.level_ok:
; Draw single digit for level
lea screen_plane,a2
add.l #LEVEL_Y*SCREEN_W+LEVEL_X/8,a2
; Get digit graphics
lsl.w #4,d0 ; *16 for font offset
lea digit_font,a0
add.w d0,a0
; Copy 8 rows, 1 byte each
moveq #7,d3
.copy_row:
move.b (a0),(a2)
addq.l #2,a0
lea SCREEN_W(a2),a2
dbf d3,.copy_row
movem.l (sp)+,d0-d4/a0-a3
rts
;------------------------------------------------------------------------------
; CALC_PIXEL_ADDR - Calculate screen address for pixel coordinates
; Input: D0 = X, D1 = Y
; Output: A2 = screen address
;------------------------------------------------------------------------------
calc_pixel_addr:
lea screen_plane,a2
move.w d1,d2
mulu #SCREEN_W,d2
add.l d2,a2
move.w d0,d2
lsr.w #3,d2
ext.l d2
add.l d2,a2
rts
;==============================================================================
; SOUND ROUTINES
;==============================================================================
play_sound:
cmp.w #SND_HOP,d0
beq.s .play_hop
cmp.w #SND_DEATH,d0
beq.s .play_death
cmp.w #SND_HOME,d0
beq.s .play_home
rts
.play_hop:
lea sound_hop,a0
move.w #HOP_LEN/2,d1
move.w #300,d2
bra.s .do_play
.play_death:
lea sound_death,a0
move.w #DEATH_LEN/2,d1
move.w #500,d2
bra.s .do_play
.play_home:
lea sound_home,a0
move.w #HOME_LEN/2,d1
move.w #200,d2
.do_play:
move.w #$0001,DMACON(a5)
move.l a0,AUD0LC(a5)
move.w d1,AUD0LEN(a5)
move.w d2,AUD0PER(a5)
move.w #64,AUD0VOL(a5)
move.w #$8001,DMACON(a5)
rts
;==============================================================================
; GAME INITIALISATION
;==============================================================================
init_game:
move.w #START_LIVES,lives
clr.l score
move.w #TIMER_START,timer ; Reset timer
move.w #1,level ; Start at level 1
lea home_filled,a0
moveq #NUM_HOMES-1,d0
.clear_homes:
clr.w (a0)+
dbf d0,.clear_homes
bsr set_car_speeds ; Set initial car speeds
bsr update_home_display
bsr reset_frog
rts
;==============================================================================
; HOME ZONE DETECTION
;==============================================================================
check_home:
move.w frog_grid_y,d0
tst.w d0
bne .not_home
move.w frog_grid_x,d0
cmp.w #HOME_0_X,d0
blt .not_home
cmp.w #HOME_0_X+2,d0
blt.s .home_0
cmp.w #HOME_1_X,d0
blt .not_home
cmp.w #HOME_1_X+2,d0
blt.s .home_1
cmp.w #HOME_2_X,d0
blt .not_home
cmp.w #HOME_2_X+2,d0
blt.s .home_2
cmp.w #HOME_3_X,d0
blt .not_home
cmp.w #HOME_3_X+2,d0
blt.s .home_3
cmp.w #HOME_4_X,d0
blt .not_home
cmp.w #HOME_4_X+2,d0
blt.s .home_4
bra .death_between
.home_0: moveq #0,d1
bra.s .check_filled
.home_1: moveq #1,d1
bra.s .check_filled
.home_2: moveq #2,d1
bra.s .check_filled
.home_3: moveq #3,d1
bra.s .check_filled
.home_4: moveq #4,d1
.check_filled:
lea home_filled,a0
add.w d1,d1
tst.w 0(a0,d1.w)
bne.s .death_filled
move.w #1,0(a0,d1.w)
add.l #POINTS_PER_HOME,score
; Time bonus: remaining seconds * 2 points
move.w timer(pc),d0
ext.l d0
divu #50,d0 ; Convert frames to seconds
and.l #$ffff,d0 ; Keep only quotient
add.l d0,d0 ; *2 for bonus
add.l d0,score ; Add time bonus
move.w #SND_HOME,d0
bsr play_sound
bsr update_home_display
bsr display_score ; Update score display
bsr check_round_complete
bsr reset_frog
rts
.death_filled:
.death_between:
bsr trigger_death
rts
.not_home:
rts
check_round_complete:
lea home_filled,a0
moveq #NUM_HOMES-1,d0
moveq #0,d1
.loop:
tst.w (a0)+
beq.s .not_complete
addq.w #1,d1
dbf d0,.loop
cmp.w #NUM_HOMES,d1
bne.s .not_complete
; All homes filled - advance to next level!
bsr next_level
.not_complete:
rts
;------------------------------------------------------------------------------
; NEXT_LEVEL - Advance to the next level
;------------------------------------------------------------------------------
next_level:
; Award level completion bonus
add.l #LEVEL_BONUS,score
; Increment level (cap at MAX_LEVEL for speed calculation)
move.w level,d0
addq.w #1,d0
move.w d0,level
; Clear all homes
lea home_filled,a0
moveq #NUM_HOMES-1,d0
.clear:
clr.w (a0)+
dbf d0,.clear
; Update car speeds for new level
bsr set_car_speeds
; Update displays
bsr update_home_display
bsr display_score
bsr display_level
rts
;------------------------------------------------------------------------------
; SET_CAR_SPEEDS - Calculate car speeds based on current level
; Speed = base_speed + (level-1) * sign(base_speed)
; This adds 1 pixel/frame for each level above 1
;------------------------------------------------------------------------------
set_car_speeds:
movem.l d0-d3/a0-a1,-(sp)
move.w level,d2
subq.w #1,d2 ; d2 = level - 1 (speed increment)
; Cap the speed increment at MAX_LEVEL-1
cmp.w #MAX_LEVEL-1,d2
ble.s .speed_ok
move.w #MAX_LEVEL-1,d2
.speed_ok:
lea base_speeds,a0
lea car_data+4,a1 ; Point to first car's speed field
moveq #NUM_CARS-1,d3
.loop:
move.w (a0)+,d0 ; Get base speed
tst.w d0
beq.s .store ; Speed 0 stays 0
bpl.s .positive
; Negative speed (moving left) - subtract increment
sub.w d2,d0
bra.s .store
.positive:
; Positive speed (moving right) - add increment
add.w d2,d0
.store:
move.w d0,(a1) ; Store new speed
addq.l #CAR_STRUCT_SIZE,a1 ; Next car's speed field
dbf d3,.loop
movem.l (sp)+,d0-d3/a0-a1
rts
update_home_display:
lea home_filled,a0
lea home_colour_0,a1
tst.w (a0)+
beq.s .home0_empty
move.w #COLOUR_HOME_FILLED,(a1)
bra.s .home1
.home0_empty:
move.w #COLOUR_HOME_LIT,(a1)
.home1:
lea home_colour_1,a1
tst.w (a0)+
beq.s .home1_empty
move.w #COLOUR_HOME_FILLED,(a1)
bra.s .home2
.home1_empty:
move.w #COLOUR_HOME_LIT,(a1)
.home2:
lea home_colour_2,a1
tst.w (a0)+
beq.s .home2_empty
move.w #COLOUR_HOME_FILLED,(a1)
bra.s .home3
.home2_empty:
move.w #COLOUR_HOME_LIT,(a1)
.home3:
lea home_colour_3,a1
tst.w (a0)+
beq.s .home3_empty
move.w #COLOUR_HOME_FILLED,(a1)
bra.s .home4
.home3_empty:
move.w #COLOUR_HOME_LIT,(a1)
.home4:
lea home_colour_4,a1
tst.w (a0)+
beq.s .home4_empty
move.w #COLOUR_HOME_FILLED,(a1)
rts
.home4_empty:
move.w #COLOUR_HOME_LIT,(a1)
rts
;==============================================================================
; LIFE DISPLAY
;==============================================================================
setup_life_sprites:
lea life_icon_1,a0
move.l a0,d0
swap d0
lea spr1pth_val,a1
move.w d0,(a1)
swap d0
lea spr1ptl_val,a1
move.w d0,(a1)
lea life_icon_2,a0
move.l a0,d0
swap d0
lea spr2pth_val,a1
move.w d0,(a1)
swap d0
lea spr2ptl_val,a1
move.w d0,(a1)
lea life_icon_3,a0
move.l a0,d0
swap d0
lea spr3pth_val,a1
move.w d0,(a1)
swap d0
lea spr3ptl_val,a1
move.w d0,(a1)
rts
update_life_display:
lea life_icon_1,a0
move.w lives,d0
cmp.w #1,d0
blt.s .hide_life1
move.w #$1e20,$0(a0)
move.w #$2600,$2(a0)
bra.s .life2
.hide_life1:
clr.l (a0)
.life2:
lea life_icon_2,a0
cmp.w #2,d0
blt.s .hide_life2
move.w #$1e28,$0(a0)
move.w #$2600,$2(a0)
bra.s .life3
.hide_life2:
clr.l (a0)
.life3:
lea life_icon_3,a0
cmp.w #3,d0
blt.s .hide_life3
move.w #$1e30,$0(a0)
move.w #$2600,$2(a0)
rts
.hide_life3:
clr.l (a0)
rts
;==============================================================================
; COLLISION AND DEATH
;==============================================================================
check_collision:
move.w frog_grid_y,d0
cmp.w #ROAD_ROW_FIRST,d0
blt .no_collision
cmp.w #ROAD_ROW_LAST,d0
bgt .no_collision
lea car_data,a2
moveq #NUM_CARS-1,d7
.loop:
move.w 2(a2),d1
cmp.w d0,d1
bne.s .next_car
move.w frog_pixel_x,d2
move.w (a2),d3
move.w d2,d4
add.w #FROG_WIDTH,d4
cmp.w d3,d4
ble.s .next_car
move.w d3,d4
add.w #CAR_WIDTH_PX,d4
cmp.w d2,d4
ble.s .next_car
bsr trigger_death
bra.s .no_collision
.next_car:
lea CAR_STRUCT_SIZE(a2),a2
dbf d7,.loop
.no_collision:
rts
trigger_death:
move.w #STATE_DYING,frog_state
move.w #DEATH_FRAMES,death_timer
move.w #FLASH_COLOUR,flash_colour
move.w #SND_DEATH,d0
bsr play_sound
subq.w #1,lives
bsr update_life_display
rts
reset_frog:
move.w #START_GRID_X,frog_grid_x
move.w #START_GRID_Y,frog_grid_y
move.w #STATE_IDLE,frog_state
clr.w frog_anim_frame
clr.w joy_prev
move.w #COLOUR_BLACK,flash_colour
move.w #TIMER_START,timer ; Reset timer for new attempt
bsr grid_to_pixels
rts
;==============================================================================
; CAR MANAGEMENT
;==============================================================================
erase_all_cars:
lea car_data,a2
moveq #NUM_CARS-1,d7
.loop:
move.w (a2),d0
move.w 2(a2),d1
bsr calc_screen_addr
bsr wait_blit
move.l a0,BLTDPTH(a5)
move.w #SCREEN_W-CAR_WIDTH*2,BLTDMOD(a5)
move.w #$0100,BLTCON0(a5)
move.w #0,BLTCON1(a5)
move.w #(CAR_HEIGHT<<6)|CAR_WIDTH,BLTSIZE(a5)
lea CAR_STRUCT_SIZE(a2),a2
dbf d7,.loop
rts
move_all_cars:
lea car_data,a2
moveq #NUM_CARS-1,d7
.loop:
move.w (a2),d0
move.w 4(a2),d1
add.w d1,d0
tst.w d1
bmi.s .check_left
cmp.w #320,d0
blt.s .store
sub.w #320+32,d0
bra.s .store
.check_left:
cmp.w #-32,d0
bgt.s .store
add.w #320+32,d0
.store:
move.w d0,(a2)
lea CAR_STRUCT_SIZE(a2),a2
dbf d7,.loop
rts
draw_all_cars:
lea car_data,a2
moveq #NUM_CARS-1,d7
.loop:
move.w (a2),d0
move.w 2(a2),d1
cmp.w #-32,d0
blt.s .next
cmp.w #320,d0
bge.s .next
bsr calc_screen_addr
bsr wait_blit
move.l #car_gfx,BLTAPTH(a5)
move.l a0,BLTDPTH(a5)
move.w #$ffff,BLTAFWM(a5)
move.w #$ffff,BLTALWM(a5)
move.w #0,BLTAMOD(a5)
move.w #SCREEN_W-CAR_WIDTH*2,BLTDMOD(a5)
move.w #$09f0,BLTCON0(a5)
move.w #0,BLTCON1(a5)
move.w #(CAR_HEIGHT<<6)|CAR_WIDTH,BLTSIZE(a5)
.next:
lea CAR_STRUCT_SIZE(a2),a2
dbf d7,.loop
rts
;==============================================================================
; FROG ROUTINES
;==============================================================================
update_frog:
move.w frog_state,d0
cmp.w #STATE_DYING,d0
beq .dying
tst.w d0
beq .idle
bra .hopping
.dying:
subq.w #1,death_timer
bgt.s .still_dying
tst.w lives
beq.s .game_over
bsr reset_frog
bra .done
.game_over:
move.w #STATE_GAMEOVER,frog_state
bra .done
.still_dying:
move.w death_timer,d0
and.w #4,d0
beq.s .flash_off
move.w #FLASH_COLOUR,flash_colour
bra .done
.flash_off:
move.w #COLOUR_BLACK,flash_colour
bra .done
.idle:
bsr read_joystick_edge
tst.w d0
beq .done
btst #8,d0
beq.s .not_up
move.w frog_grid_y,d1
tst.w d1
beq.s .not_up
move.w #DIR_UP,frog_dir
bra.s .start_hop
.not_up:
btst #0,d0
beq.s .not_down
move.w frog_grid_y,d1
cmp.w #GRID_ROWS-1,d1
beq.s .not_down
move.w #DIR_DOWN,frog_dir
bra.s .start_hop
.not_down:
btst #9,d0
beq.s .not_left
move.w frog_grid_x,d1
tst.w d1
beq.s .not_left
move.w #DIR_LEFT,frog_dir
bra.s .start_hop
.not_left:
btst #1,d0
beq .done
move.w frog_grid_x,d1
cmp.w #GRID_COLS-1,d1
beq .done
move.w #DIR_RIGHT,frog_dir
.start_hop:
move.w #STATE_HOPPING,frog_state
clr.w frog_anim_frame
move.w #SND_HOP,d0
bsr play_sound
bra.s .done
.hopping:
addq.w #1,frog_anim_frame
move.w frog_dir,d0
cmp.w #DIR_UP,d0
bne.s .hop_not_up
sub.w #PIXELS_PER_FRAME,frog_pixel_y
bra.s .check_done
.hop_not_up:
cmp.w #DIR_DOWN,d0
bne.s .hop_not_down
add.w #PIXELS_PER_FRAME,frog_pixel_y
bra.s .check_done
.hop_not_down:
cmp.w #DIR_LEFT,d0
bne.s .hop_not_left
sub.w #PIXELS_PER_FRAME,frog_pixel_x
bra.s .check_done
.hop_not_left:
add.w #PIXELS_PER_FRAME,frog_pixel_x
.check_done:
cmp.w #HOP_FRAMES,frog_anim_frame
blt.s .done
move.w frog_dir,d0
cmp.w #DIR_UP,d0
bne.s .end_not_up
subq.w #1,frog_grid_y
bra.s .snap
.end_not_up:
cmp.w #DIR_DOWN,d0
bne.s .end_not_down
addq.w #1,frog_grid_y
bra.s .snap
.end_not_down:
cmp.w #DIR_LEFT,d0
bne.s .end_not_left
subq.w #1,frog_grid_x
bra.s .snap
.end_not_left:
addq.w #1,frog_grid_x
.snap:
bsr grid_to_pixels
move.w #STATE_IDLE,frog_state
.done:
move.w flash_colour,flash_copper
rts
;==============================================================================
; UTILITY ROUTINES
;==============================================================================
grid_to_pixels:
move.w frog_grid_x,d0
mulu #CELL_SIZE,d0
add.w #GRID_ORIGIN_X,d0
move.w d0,frog_pixel_x
move.w frog_grid_y,d0
mulu #CELL_SIZE,d0
add.w #GRID_ORIGIN_Y,d0
move.w d0,frog_pixel_y
rts
read_joystick_edge:
move.w JOY1DAT(a5),d0
move.w d0,d1
lsr.w #1,d1
eor.w d1,d0
move.w joy_prev,d1
not.w d1
and.w d0,d1
move.w d0,joy_prev
move.w d1,d0
rts
wait_vblank:
move.l #$1ff00,d1
.wait:
move.l VPOSR(a5),d0
and.l d1,d0
bne.s .wait
rts
wait_blit:
btst #6,DMACONR(a5)
bne.s wait_blit
rts
clear_screen:
bsr.s wait_blit
move.l #screen_plane,BLTDPTH(a5)
move.w #0,BLTDMOD(a5)
move.w #$0100,BLTCON0(a5)
move.w #0,BLTCON1(a5)
move.w #(SCREEN_H<<6)|SCREEN_W/2,BLTSIZE(a5)
rts
calc_screen_addr:
lea screen_plane,a0
move.w d1,d2
mulu #CELL_SIZE,d2
add.w #GRID_ORIGIN_Y,d2
mulu #SCREEN_W,d2
add.l d2,a0
move.w d0,d2
lsr.w #3,d2
ext.l d2
add.l d2,a0
rts
update_sprite:
lea frog_data,a0
move.w frog_pixel_y,d0
move.w frog_pixel_x,d1
move.w d0,d2
lsl.w #8,d2
lsr.w #1,d1
or.b d1,d2
move.w d2,(a0)
add.w #FROG_HEIGHT,d0
lsl.w #8,d0
move.w d0,2(a0)
rts
;==============================================================================
; VARIABLES
;==============================================================================
frog_grid_x: dc.w 9
frog_grid_y: dc.w 12
frog_pixel_x: dc.w 0
frog_pixel_y: dc.w 0
frog_state: dc.w 0
frog_dir: dc.w 0
frog_anim_frame: dc.w 0
joy_prev: dc.w 0
death_timer: dc.w 0
flash_colour: dc.w 0
lives: dc.w 3
score: dc.l 0
timer: dc.w 3000 ; Countdown timer in frames
level: dc.w 1 ; Current level (1-8+)
game_state: dc.w 0 ; High-level game state (title/playing/over)
fire_prev: dc.w 0 ; Previous fire button state for edge detection
home_filled: dc.w 0,0,0,0,0
; Buffer for score digits
score_digits: dc.w 0,0,0,0,0,0
; Buffer for timer digits (2 digits for seconds)
timer_digits: dc.w 0,0
car_data:
dc.w 0,7,1,0
dc.w 160,7,1,0
dc.w 100,8,-2,0
dc.w 250,8,-2,0
dc.w 50,9,2,0
dc.w 200,9,2,0
dc.w 80,10,-1,0
dc.w 220,10,-1,0
dc.w 30,11,3,0
dc.w 180,11,3,0
; Base speeds for cars (used to calculate speed per level)
base_speeds:
dc.w 1 ; Car 0: right, slow
dc.w 1 ; Car 1: right, slow
dc.w -2 ; Car 2: left, medium
dc.w -2 ; Car 3: left, medium
dc.w 2 ; Car 4: right, medium
dc.w 2 ; Car 5: right, medium
dc.w -1 ; Car 6: left, slow
dc.w -1 ; Car 7: left, slow
dc.w 3 ; Car 8: right, fast
dc.w 3 ; Car 9: right, fast
;==============================================================================
; COPPER LIST
;==============================================================================
copperlist:
dc.w COLOR00
flash_copper:
dc.w COLOUR_BLACK
dc.w $0100,$1200
dc.w $0102,$0000
dc.w $0104,$0000
dc.w $0108,$0000
dc.w $010a,$0000
dc.w $00e0
bplpth_val: dc.w $0000
dc.w $00e2
bplptl_val: dc.w $0000
dc.w $0180,$0000
dc.w $0182,COLOUR_CAR
dc.w $01a2,COLOUR_FROG
dc.w $01a4,COLOUR_EYES
dc.w $01a6,COLOUR_OUTLINE
dc.w SPR0PTH
sprpth_val: dc.w $0000
dc.w SPR0PTL
sprptl_val: dc.w $0000
dc.w SPR1PTH
spr1pth_val: dc.w $0000
dc.w SPR1PTL
spr1ptl_val: dc.w $0000
dc.w SPR2PTH
spr2pth_val: dc.w $0000
dc.w SPR2PTL
spr2ptl_val: dc.w $0000
dc.w $0126
spr3pth_val: dc.w $0000
dc.w $012a
spr3ptl_val: dc.w $0000
; Home zone row
dc.w $2c07,$fffe
dc.w COLOR00,COLOUR_HOME
dc.w $2c4f,$fffe
dc.w COLOR00
home_colour_0:
dc.w COLOUR_HOME_LIT
dc.w $2c5f,$fffe
dc.w COLOR00,COLOUR_HOME
dc.w $2c8f,$fffe
dc.w COLOR00
home_colour_1:
dc.w COLOUR_HOME_LIT
dc.w $2c9f,$fffe
dc.w COLOR00,COLOUR_HOME
dc.w $2ccf,$fffe
dc.w COLOR00
home_colour_2:
dc.w COLOUR_HOME_LIT
dc.w $2cdf,$fffe
dc.w COLOR00,COLOUR_HOME
dc.w $2d07,$fffe
dc.w COLOR00
home_colour_3:
dc.w COLOUR_HOME_LIT
dc.w $2d17,$fffe
dc.w COLOR00,COLOUR_HOME
dc.w $2d47,$fffe
dc.w COLOR00
home_colour_4:
dc.w COLOUR_HOME_LIT
dc.w $2d57,$fffe
dc.w COLOR00,COLOUR_HOME
dc.w $3407,$fffe
dc.w COLOR00,COLOUR_HOME_LIT
dc.w $3807,$fffe
dc.w COLOR00,COLOUR_HOME
dc.w $3c07,$fffe
dc.w COLOR00,COLOUR_WATER1
dc.w $4c07,$fffe
dc.w COLOR00,COLOUR_WATER2
dc.w $5c07,$fffe
dc.w COLOR00,COLOUR_WATER1
dc.w $6c07,$fffe
dc.w COLOR00,COLOUR_WATER2
dc.w $7c07,$fffe
dc.w COLOR00,COLOUR_WATER1
dc.w $8c07,$fffe
dc.w COLOR00,COLOUR_MEDIAN
dc.w $9c07,$fffe
dc.w COLOR00,COLOUR_ROAD1
dc.w $ac07,$fffe
dc.w COLOR00,COLOUR_ROAD2
dc.w $bc07,$fffe
dc.w COLOR00,COLOUR_ROAD1
dc.w $cc07,$fffe
dc.w COLOR00,COLOUR_ROAD2
dc.w $dc07,$fffe
dc.w COLOR00,COLOUR_ROAD1
dc.w $ec07,$fffe
dc.w COLOR00,COLOUR_START
dc.w $f407,$fffe
dc.w COLOR00,COLOUR_START_LIT
dc.w $f807,$fffe
dc.w COLOR00,COLOUR_START
dc.w $fc07,$fffe
dc.w COLOR00,COLOUR_BLACK
dc.w $ffff,$fffe
;==============================================================================
; GRAPHICS DATA
;==============================================================================
even
car_gfx:
dc.w $0ff0,$0ff0
dc.w $3ffc,$3ffc
dc.w $7ffe,$7ffe
dc.w $ffff,$ffff
dc.w $ffff,$ffff
dc.w $ffff,$ffff
dc.w $ffff,$ffff
dc.w $ffff,$ffff
dc.w $ffff,$ffff
dc.w $7ffe,$7ffe
dc.w $3c3c,$3c3c
dc.w $0000,$0000
even
frog_data:
dc.w $ec50,$fc00
dc.w $0000,$0000
dc.w $07e0,$0000
dc.w $1ff8,$0420
dc.w $3ffc,$0a50
dc.w $7ffe,$1248
dc.w $7ffe,$1008
dc.w $ffff,$2004
dc.w $ffff,$0000
dc.w $ffff,$0000
dc.w $7ffe,$2004
dc.w $7ffe,$1008
dc.w $3ffc,$0810
dc.w $1ff8,$0420
dc.w $07e0,$0000
dc.w $0000,$0000
dc.w $0000,$0000
dc.w $0000,$0000
even
life_icon_1:
dc.w $0000,$0000
dc.w $0000,$0000
dc.w $1800,$0000
dc.w $3c00,$0000
dc.w $7e00,$0000
dc.w $7e00,$0000
dc.w $3c00,$0000
dc.w $1800,$0000
dc.w $0000,$0000
dc.w $0000,$0000
even
life_icon_2:
dc.w $0000,$0000
dc.w $0000,$0000
dc.w $1800,$0000
dc.w $3c00,$0000
dc.w $7e00,$0000
dc.w $7e00,$0000
dc.w $3c00,$0000
dc.w $1800,$0000
dc.w $0000,$0000
dc.w $0000,$0000
even
life_icon_3:
dc.w $0000,$0000
dc.w $0000,$0000
dc.w $1800,$0000
dc.w $3c00,$0000
dc.w $7e00,$0000
dc.w $7e00,$0000
dc.w $3c00,$0000
dc.w $1800,$0000
dc.w $0000,$0000
dc.w $0000,$0000
; Digit font (in Chip RAM via code_c section)
even
digit_font:
; 0
dc.w $3c00
dc.w $6600
dc.w $6e00
dc.w $7e00
dc.w $7600
dc.w $6600
dc.w $3c00
dc.w $0000
; 1
dc.w $1800
dc.w $3800
dc.w $1800
dc.w $1800
dc.w $1800
dc.w $1800
dc.w $7e00
dc.w $0000
; 2
dc.w $3c00
dc.w $6600
dc.w $0600
dc.w $1c00
dc.w $3000
dc.w $6000
dc.w $7e00
dc.w $0000
; 3
dc.w $3c00
dc.w $6600
dc.w $0600
dc.w $1c00
dc.w $0600
dc.w $6600
dc.w $3c00
dc.w $0000
; 4
dc.w $0c00
dc.w $1c00
dc.w $3c00
dc.w $6c00
dc.w $7e00
dc.w $0c00
dc.w $0c00
dc.w $0000
; 5
dc.w $7e00
dc.w $6000
dc.w $7c00
dc.w $0600
dc.w $0600
dc.w $6600
dc.w $3c00
dc.w $0000
; 6
dc.w $1c00
dc.w $3000
dc.w $6000
dc.w $7c00
dc.w $6600
dc.w $6600
dc.w $3c00
dc.w $0000
; 7
dc.w $7e00
dc.w $0600
dc.w $0c00
dc.w $1800
dc.w $3000
dc.w $3000
dc.w $3000
dc.w $0000
; 8
dc.w $3c00
dc.w $6600
dc.w $6600
dc.w $3c00
dc.w $6600
dc.w $6600
dc.w $3c00
dc.w $0000
; 9
dc.w $3c00
dc.w $6600
dc.w $6600
dc.w $3e00
dc.w $0600
dc.w $0c00
dc.w $3800
dc.w $0000
; Letter font for title/game over text
; Letters indexed: A=0, E=1, G=2, I=3, L=4, M=5, N=6, O=7, R=8, S=9, V=10
even
letter_font:
; A (index 0)
dc.w $3c00
dc.w $6600
dc.w $6600
dc.w $7e00
dc.w $6600
dc.w $6600
dc.w $6600
dc.w $0000
; E (index 1)
dc.w $7e00
dc.w $6000
dc.w $6000
dc.w $7c00
dc.w $6000
dc.w $6000
dc.w $7e00
dc.w $0000
; G (index 2)
dc.w $3c00
dc.w $6600
dc.w $6000
dc.w $6e00
dc.w $6600
dc.w $6600
dc.w $3c00
dc.w $0000
; I (index 3)
dc.w $7e00
dc.w $1800
dc.w $1800
dc.w $1800
dc.w $1800
dc.w $1800
dc.w $7e00
dc.w $0000
; L (index 4)
dc.w $6000
dc.w $6000
dc.w $6000
dc.w $6000
dc.w $6000
dc.w $6000
dc.w $7e00
dc.w $0000
; M (index 5)
dc.w $c600
dc.w $ee00
dc.w $fe00
dc.w $d600
dc.w $c600
dc.w $c600
dc.w $c600
dc.w $0000
; N (index 6)
dc.w $6600
dc.w $7600
dc.w $7e00
dc.w $7e00
dc.w $6e00
dc.w $6600
dc.w $6600
dc.w $0000
; O (index 7)
dc.w $3c00
dc.w $6600
dc.w $6600
dc.w $6600
dc.w $6600
dc.w $6600
dc.w $3c00
dc.w $0000
; R (index 8)
dc.w $7c00
dc.w $6600
dc.w $6600
dc.w $7c00
dc.w $6c00
dc.w $6600
dc.w $6600
dc.w $0000
; S (index 9)
dc.w $3c00
dc.w $6600
dc.w $6000
dc.w $3c00
dc.w $0600
dc.w $6600
dc.w $3c00
dc.w $0000
; V (index 10)
dc.w $6600
dc.w $6600
dc.w $6600
dc.w $6600
dc.w $6600
dc.w $3c00
dc.w $1800
dc.w $0000
; Text data - "SIGNAL" (S=9, I=3, G=2, N=6, A=0, L=4)
title_text:
dc.w 9,3,2,6,0,4
; Text data - "GAME OVER" (G=2, A=0, M=5, E=1, space=99, O=7, V=10, E=1, R=8)
gameover_text:
dc.w 2,0,5,1,99,7,10,1,8
;==============================================================================
; SOUND DATA (must be in Chip RAM for Paula DMA)
;==============================================================================
even
sound_hop:
dc.b $7f,$7f,$7f,$7f,$7f,$7f,$7f,$7f
dc.b $80,$80,$80,$80,$80,$80,$80,$80
dc.b $7f,$7f,$7f,$7f,$7f,$7f,$7f,$7f
dc.b $80,$80,$80,$80,$80,$80,$80,$80
HOP_LEN equ *-sound_hop
sound_death:
dc.b $7f,$7f,$7f,$7f,$80,$80,$80,$80
dc.b $7f,$7f,$7f,$7f,$80,$80,$80,$80
dc.b $7f,$7f,$7f,$7f,$7f,$80,$80,$80,$80,$80
dc.b $7f,$7f,$7f,$7f,$7f,$7f,$80,$80,$80,$80,$80,$80
dc.b $7f,$7f,$7f,$7f,$7f,$7f,$7f,$7f
dc.b $80,$80,$80,$80,$80,$80,$80,$80
DEATH_LEN equ *-sound_death
sound_home:
dc.b $7f,$80,$7f,$80,$7f,$80,$7f,$80
dc.b $7f,$80,$7f,$80,$7f,$80,$7f,$80
dc.b $7f,$7f,$80,$80,$7f,$7f,$80,$80
dc.b $7f,$7f,$80,$80,$7f,$7f,$80,$80
dc.b $7f,$7f,$7f,$80,$80,$80,$7f,$7f,$7f,$80,$80,$80
dc.b $00,$00,$00,$00
HOME_LEN equ *-sound_home
;==============================================================================
; SCREEN BUFFER
;==============================================================================
section chipbss,bss_c
even
screen_plane:
ds.b PLANE_SIZE
Build It
vasmm68k_mot -Fhunkexe -kick1hunks -o signal signal.asmWhat’s Next
In Unit 16, we’ll complete Phase 1 with final polish—high score tracking and presentation refinements.
What Changed
Unit 14 → Unit 15
+264-14
| 1 | 1 | ;============================================================================== | |
| 2 | 2 | ; SIGNAL - A Frogger-style game for the Commodore Amiga | |
| 3 | - | ; Unit 14: Level Progression | |
| 3 | + | ; Unit 15: Game States | |
| 4 | 4 | ; | |
| 5 | - | ; Fill all 5 homes to complete a level. Each new level increases difficulty - | |
| 6 | - | ; cars move faster. Progress through levels for higher scores. | |
| 5 | + | ; A complete game needs proper flow: title screen, gameplay, game over. | |
| 6 | + | ; This unit adds a state machine that manages these transitions. | |
| 7 | 7 | ;============================================================================== | |
| 8 | 8 | | |
| 9 | 9 | ;============================================================================== | |
| ... | |||
| 76 | 76 | LEVEL_X equ 152 ; Pixel X position for level display (centre) | |
| 77 | 77 | LEVEL_Y equ 236 ; Same row as score/timer | |
| 78 | 78 | LEVEL_BONUS equ 100 ; Bonus points per level complete | |
| 79 | + | | |
| 80 | + | ; Game state constants (high-level game flow) | |
| 81 | + | GSTATE_TITLE equ 0 ; Title screen, waiting for fire | |
| 82 | + | GSTATE_PLAYING equ 1 ; Active gameplay | |
| 83 | + | GSTATE_OVER equ 2 ; Game over screen | |
| 84 | + | | |
| 85 | + | ; Title screen position | |
| 86 | + | TITLE_Y equ 100 ; Vertical position for "SIGNAL" text | |
| 79 | 87 | | |
| 80 | 88 | ; Audio constants | |
| 81 | 89 | SND_HOP equ 0 | |
| ... | |||
| 195 | 203 | | |
| 196 | 204 | move.w #$87e1,DMACON(a5) | |
| 197 | 205 | | |
| 198 | - | ; Display score, timer, and level after all DMA enabled | |
| 199 | - | bsr display_score | |
| 200 | - | bsr display_timer | |
| 201 | - | bsr display_level | |
| 206 | + | ; Start at title screen | |
| 207 | + | move.w #GSTATE_TITLE,game_state | |
| 208 | + | bsr show_title | |
| 202 | 209 | | |
| 203 | 210 | ;============================================================================== | |
| 204 | - | ; MAIN LOOP | |
| 211 | + | ; MAIN LOOP - Dispatches based on game_state | |
| 205 | 212 | ;============================================================================== | |
| 206 | 213 | | |
| 207 | 214 | mainloop: | |
| 208 | 215 | bsr wait_vblank | |
| 209 | 216 | | |
| 210 | - | cmp.w #STATE_GAMEOVER,frog_state | |
| 211 | - | beq .game_over_loop | |
| 217 | + | move.w game_state,d0 | |
| 218 | + | cmp.w #GSTATE_TITLE,d0 | |
| 219 | + | beq title_loop | |
| 220 | + | cmp.w #GSTATE_OVER,d0 | |
| 221 | + | beq gameover_loop | |
| 212 | 222 | | |
| 223 | + | ; GSTATE_PLAYING - active gameplay | |
| 213 | 224 | bsr update_frog | |
| 214 | 225 | bsr update_sprite | |
| 226 | + | | |
| 227 | + | ; Check if frog died (transition to game over) | |
| 228 | + | cmp.w #STATE_GAMEOVER,frog_state | |
| 229 | + | beq .enter_gameover | |
| 215 | 230 | | |
| 216 | 231 | ; Update timer (only when not dying) | |
| 217 | 232 | cmp.w #STATE_DYING,frog_state | |
| ... | |||
| 233 | 248 | | |
| 234 | 249 | bra mainloop | |
| 235 | 250 | | |
| 236 | - | .game_over_loop: | |
| 237 | - | btst #7,$bfe001 | |
| 238 | - | bne.s mainloop | |
| 251 | + | .enter_gameover: | |
| 252 | + | move.w #GSTATE_OVER,game_state | |
| 253 | + | bsr show_gameover | |
| 254 | + | bra mainloop | |
| 255 | + | | |
| 256 | + | ;------------------------------------------------------------------------------ | |
| 257 | + | ; TITLE_LOOP - Wait for fire button on title screen | |
| 258 | + | ;------------------------------------------------------------------------------ | |
| 259 | + | title_loop: | |
| 260 | + | bsr read_fire_edge | |
| 261 | + | tst.w d0 | |
| 262 | + | beq mainloop ; No fire press, keep waiting | |
| 239 | 263 | | |
| 264 | + | ; Fire pressed - start game! | |
| 265 | + | move.w #GSTATE_PLAYING,game_state | |
| 240 | 266 | bsr init_game | |
| 267 | + | bsr clear_screen | |
| 241 | 268 | bsr update_life_display | |
| 242 | 269 | bsr display_score | |
| 243 | 270 | bsr display_timer | |
| 244 | 271 | bsr display_level | |
| 245 | - | bsr clear_screen | |
| 272 | + | bsr update_sprite | |
| 273 | + | bra mainloop | |
| 274 | + | | |
| 275 | + | ;------------------------------------------------------------------------------ | |
| 276 | + | ; GAMEOVER_LOOP - Wait for fire button on game over screen | |
| 277 | + | ;------------------------------------------------------------------------------ | |
| 278 | + | gameover_loop: | |
| 279 | + | bsr read_fire_edge | |
| 280 | + | tst.w d0 | |
| 281 | + | beq mainloop ; No fire press, keep waiting | |
| 246 | 282 | | |
| 283 | + | ; Fire pressed - return to title | |
| 284 | + | move.w #GSTATE_TITLE,game_state | |
| 285 | + | bsr clear_screen | |
| 286 | + | bsr show_title | |
| 247 | 287 | bra mainloop | |
| 288 | + | | |
| 289 | + | ;------------------------------------------------------------------------------ | |
| 290 | + | ; READ_FIRE_EDGE - Detect fire button press (edge triggered) | |
| 291 | + | ; Returns: D0 = 1 if fire just pressed, 0 otherwise | |
| 292 | + | ;------------------------------------------------------------------------------ | |
| 293 | + | read_fire_edge: | |
| 294 | + | btst #7,$bfe001 ; Fire button (active low) | |
| 295 | + | seq d0 ; D0 = $FF if pressed, $00 if not | |
| 296 | + | and.w #1,d0 ; D0 = 1 if pressed | |
| 297 | + | move.w fire_prev,d1 | |
| 298 | + | move.w d0,fire_prev | |
| 299 | + | not.w d1 ; D1 = 1 if was NOT pressed | |
| 300 | + | and.w d1,d0 ; D0 = 1 only on rising edge | |
| 301 | + | rts | |
| 302 | + | | |
| 303 | + | ;------------------------------------------------------------------------------ | |
| 304 | + | ; SHOW_TITLE - Display title screen | |
| 305 | + | ;------------------------------------------------------------------------------ | |
| 306 | + | show_title: | |
| 307 | + | bsr clear_screen | |
| 308 | + | bsr wait_blit | |
| 309 | + | | |
| 310 | + | ; Hide frog sprite during title | |
| 311 | + | lea frog_data,a0 | |
| 312 | + | clr.l (a0) | |
| 313 | + | | |
| 314 | + | ; Hide life sprites | |
| 315 | + | lea life_icon_1,a0 | |
| 316 | + | clr.l (a0) | |
| 317 | + | lea life_icon_2,a0 | |
| 318 | + | clr.l (a0) | |
| 319 | + | lea life_icon_3,a0 | |
| 320 | + | clr.l (a0) | |
| 321 | + | | |
| 322 | + | ; Draw "SIGNAL" text centred on screen | |
| 323 | + | ; Each letter is 8 pixels wide, "SIGNAL" = 6 letters = 48 pixels | |
| 324 | + | ; Centre: (320-48)/2 = 136 pixels = 17 bytes | |
| 325 | + | lea screen_plane,a2 | |
| 326 | + | add.l #TITLE_Y*SCREEN_W+17,a2 | |
| 327 | + | | |
| 328 | + | lea title_text,a1 | |
| 329 | + | moveq #5,d4 ; 6 letters | |
| 330 | + | | |
| 331 | + | .draw_letter: | |
| 332 | + | move.w (a1)+,d0 ; Get letter index | |
| 333 | + | lsl.w #4,d0 ; *16 for font offset | |
| 334 | + | lea letter_font,a0 | |
| 335 | + | add.w d0,a0 | |
| 336 | + | | |
| 337 | + | move.l a2,a3 | |
| 338 | + | moveq #7,d3 | |
| 339 | + | .copy_row: | |
| 340 | + | move.b (a0),(a3) | |
| 341 | + | addq.l #2,a0 | |
| 342 | + | lea SCREEN_W(a3),a3 | |
| 343 | + | dbf d3,.copy_row | |
| 344 | + | | |
| 345 | + | addq.l #1,a2 | |
| 346 | + | dbf d4,.draw_letter | |
| 347 | + | | |
| 348 | + | rts | |
| 349 | + | | |
| 350 | + | ;------------------------------------------------------------------------------ | |
| 351 | + | ; SHOW_GAMEOVER - Display game over screen with final score | |
| 352 | + | ;------------------------------------------------------------------------------ | |
| 353 | + | show_gameover: | |
| 354 | + | ; Keep the game screen visible but draw "GAME OVER" text | |
| 355 | + | ; Draw at centre of screen | |
| 356 | + | lea screen_plane,a2 | |
| 357 | + | add.l #120*SCREEN_W+15,a2 ; Centre "GAME OVER" (9 chars = 72px) | |
| 358 | + | | |
| 359 | + | lea gameover_text,a1 | |
| 360 | + | moveq #8,d4 ; 9 characters (including space) | |
| 361 | + | | |
| 362 | + | .draw_letter: | |
| 363 | + | move.w (a1)+,d0 | |
| 364 | + | cmp.w #99,d0 ; 99 = space | |
| 365 | + | beq.s .space | |
| 366 | + | lsl.w #4,d0 | |
| 367 | + | lea letter_font,a0 | |
| 368 | + | add.w d0,a0 | |
| 369 | + | | |
| 370 | + | move.l a2,a3 | |
| 371 | + | moveq #7,d3 | |
| 372 | + | .copy_row: | |
| 373 | + | move.b (a0),(a3) | |
| 374 | + | addq.l #2,a0 | |
| 375 | + | lea SCREEN_W(a3),a3 | |
| 376 | + | dbf d3,.copy_row | |
| 377 | + | | |
| 378 | + | .space: | |
| 379 | + | ; Space or after drawing - advance to next position | |
| 380 | + | addq.l #1,a2 | |
| 381 | + | dbf d4,.draw_letter | |
| 382 | + | | |
| 383 | + | rts | |
| 248 | 384 | | |
| 249 | 385 | ;============================================================================== | |
| 250 | 386 | ; SCORE DISPLAY | |
| ... | |||
| 1142 | 1278 | score: dc.l 0 | |
| 1143 | 1279 | timer: dc.w 3000 ; Countdown timer in frames | |
| 1144 | 1280 | level: dc.w 1 ; Current level (1-8+) | |
| 1281 | + | game_state: dc.w 0 ; High-level game state (title/playing/over) | |
| 1282 | + | fire_prev: dc.w 0 ; Previous fire button state for edge detection | |
| 1145 | 1283 | | |
| 1146 | 1284 | home_filled: dc.w 0,0,0,0,0 | |
| 1147 | 1285 | | |
| ... | |||
| 1482 | 1620 | dc.w $0600 | |
| 1483 | 1621 | dc.w $0c00 | |
| 1484 | 1622 | dc.w $3800 | |
| 1623 | + | dc.w $0000 | |
| 1624 | + | | |
| 1625 | + | ; Letter font for title/game over text | |
| 1626 | + | ; Letters indexed: A=0, E=1, G=2, I=3, L=4, M=5, N=6, O=7, R=8, S=9, V=10 | |
| 1627 | + | even | |
| 1628 | + | letter_font: | |
| 1629 | + | ; A (index 0) | |
| 1630 | + | dc.w $3c00 | |
| 1631 | + | dc.w $6600 | |
| 1632 | + | dc.w $6600 | |
| 1633 | + | dc.w $7e00 | |
| 1634 | + | dc.w $6600 | |
| 1635 | + | dc.w $6600 | |
| 1636 | + | dc.w $6600 | |
| 1637 | + | dc.w $0000 | |
| 1638 | + | ; E (index 1) | |
| 1639 | + | dc.w $7e00 | |
| 1640 | + | dc.w $6000 | |
| 1641 | + | dc.w $6000 | |
| 1642 | + | dc.w $7c00 | |
| 1643 | + | dc.w $6000 | |
| 1644 | + | dc.w $6000 | |
| 1645 | + | dc.w $7e00 | |
| 1646 | + | dc.w $0000 | |
| 1647 | + | ; G (index 2) | |
| 1648 | + | dc.w $3c00 | |
| 1649 | + | dc.w $6600 | |
| 1650 | + | dc.w $6000 | |
| 1651 | + | dc.w $6e00 | |
| 1652 | + | dc.w $6600 | |
| 1653 | + | dc.w $6600 | |
| 1654 | + | dc.w $3c00 | |
| 1655 | + | dc.w $0000 | |
| 1656 | + | ; I (index 3) | |
| 1657 | + | dc.w $7e00 | |
| 1658 | + | dc.w $1800 | |
| 1659 | + | dc.w $1800 | |
| 1660 | + | dc.w $1800 | |
| 1661 | + | dc.w $1800 | |
| 1662 | + | dc.w $1800 | |
| 1663 | + | dc.w $7e00 | |
| 1664 | + | dc.w $0000 | |
| 1665 | + | ; L (index 4) | |
| 1666 | + | dc.w $6000 | |
| 1667 | + | dc.w $6000 | |
| 1668 | + | dc.w $6000 | |
| 1669 | + | dc.w $6000 | |
| 1670 | + | dc.w $6000 | |
| 1671 | + | dc.w $6000 | |
| 1672 | + | dc.w $7e00 | |
| 1673 | + | dc.w $0000 | |
| 1674 | + | ; M (index 5) | |
| 1675 | + | dc.w $c600 | |
| 1676 | + | dc.w $ee00 | |
| 1677 | + | dc.w $fe00 | |
| 1678 | + | dc.w $d600 | |
| 1679 | + | dc.w $c600 | |
| 1680 | + | dc.w $c600 | |
| 1681 | + | dc.w $c600 | |
| 1682 | + | dc.w $0000 | |
| 1683 | + | ; N (index 6) | |
| 1684 | + | dc.w $6600 | |
| 1685 | + | dc.w $7600 | |
| 1686 | + | dc.w $7e00 | |
| 1687 | + | dc.w $7e00 | |
| 1688 | + | dc.w $6e00 | |
| 1689 | + | dc.w $6600 | |
| 1690 | + | dc.w $6600 | |
| 1691 | + | dc.w $0000 | |
| 1692 | + | ; O (index 7) | |
| 1693 | + | dc.w $3c00 | |
| 1694 | + | dc.w $6600 | |
| 1695 | + | dc.w $6600 | |
| 1696 | + | dc.w $6600 | |
| 1697 | + | dc.w $6600 | |
| 1698 | + | dc.w $6600 | |
| 1699 | + | dc.w $3c00 | |
| 1700 | + | dc.w $0000 | |
| 1701 | + | ; R (index 8) | |
| 1702 | + | dc.w $7c00 | |
| 1703 | + | dc.w $6600 | |
| 1704 | + | dc.w $6600 | |
| 1705 | + | dc.w $7c00 | |
| 1706 | + | dc.w $6c00 | |
| 1707 | + | dc.w $6600 | |
| 1708 | + | dc.w $6600 | |
| 1709 | + | dc.w $0000 | |
| 1710 | + | ; S (index 9) | |
| 1711 | + | dc.w $3c00 | |
| 1712 | + | dc.w $6600 | |
| 1713 | + | dc.w $6000 | |
| 1714 | + | dc.w $3c00 | |
| 1715 | + | dc.w $0600 | |
| 1716 | + | dc.w $6600 | |
| 1717 | + | dc.w $3c00 | |
| 1718 | + | dc.w $0000 | |
| 1719 | + | ; V (index 10) | |
| 1720 | + | dc.w $6600 | |
| 1721 | + | dc.w $6600 | |
| 1722 | + | dc.w $6600 | |
| 1723 | + | dc.w $6600 | |
| 1724 | + | dc.w $6600 | |
| 1725 | + | dc.w $3c00 | |
| 1726 | + | dc.w $1800 | |
| 1485 | 1727 | dc.w $0000 | |
| 1728 | + | | |
| 1729 | + | ; Text data - "SIGNAL" (S=9, I=3, G=2, N=6, A=0, L=4) | |
| 1730 | + | title_text: | |
| 1731 | + | dc.w 9,3,2,6,0,4 | |
| 1732 | + | | |
| 1733 | + | ; Text data - "GAME OVER" (G=2, A=0, M=5, E=1, space=99, O=7, V=10, E=1, R=8) | |
| 1734 | + | gameover_text: | |
| 1735 | + | dc.w 2,0,5,1,99,7,10,1,8 | |
| 1486 | 1736 | | |
| 1487 | 1737 | ;============================================================================== | |
| 1488 | 1738 | ; SOUND DATA (must be in Chip RAM for Paula DMA) |