Game 1 Unit 16 of 64 1 hr learning time

Phase 1 Complete

Review Phase 1 and preview what comes next. Roads-only Frogger complete.

25% of Signal

Mark as complete Completed!

What You Built

A complete Amiga game. From nothing to playable in 16 units.

Phase 1 Complete

Title screen. Press fire. Gameplay with traffic to avoid. Lives and scoring. Timer counting down. Level progression with increasing speed. Game over. Return to title. Complete flow.

See It In Action

Signal gameplay — navigate the frog across busy roads while avoiding traffic

You built this on the Commodore Amiga—a machine designed in 1985. Using the same hardware registers that developers used back then. No modern abstractions. Pure metal.

Phase 1 Summary

Unit	Topic	What You Built
1	Hello Amiga	Copper display and hardware sprite
2	Moving the Frog	Joystick input and movement
3	Understanding What We Built	Deep dive into scaffold
4	The Playfield	Zone colours with Copper
5	Grid-Based Movement	Discrete hopping
6	The Blitter Introduction	DMA graphics engine
7	Cars on the Road	Blitter-drawn traffic
8	Collision Detection	Death and respawn
9	Lives System	Stakes and game over
10	Home Zones	Goals and scoring
11	Sound Effects	Paula audio
12	Score Display	HUD rendering
13	Timer	Urgency and bonuses
14	Level Progression	Difficulty scaling
15	Game States	Complete game flow
16	Phase 1 Complete	Review and polish

The Custom Chipset

You’ve now used all four custom chips:

Agnus (the Blitter)

Erasing car rectangles
Drawing car graphics
Clearing the screen
Rendering score/timer digits

Denise (display)

1-bitplane mode for cars
Hardware sprites for frog and lives
Colour registers for all game elements

Paula (audio)

Hop sound on movement
Death sound on collision
Home sound on reaching goal

Copper (display processor)

Per-scanline colour changes
Home zone detection colours
Playfield zone backgrounds
Sprite pointer setup

Here’s a quick reference of how we used each chip:

; Phase 1 Custom Chipset Summary
; ==============================

; AGNUS (Blitter)
; ---------------
; Used for: car drawing, screen clearing, digit rendering
move.w  #$0100,BLTCON0(a5)          ; Clear mode (D = 0)
move.w  #$09f0,BLTCON0(a5)          ; Copy mode (D = A)

; DENISE (Display)
; ----------------
; Used for: bitplane display, sprites, colours
            dc.w    $0100,$1200     ; 1 bitplane, colour enabled
            dc.w    $0182,COLOUR_CAR ; Colour 1 = red for cars
            dc.w    $01a2,COLOUR_FROG ; Sprite colour 1 = green

; PAULA (Audio)
; -------------
; Used for: hop, death, home sounds
move.l  a0,AUD0LC(a5)               ; Sample address
move.w  d1,AUD0LEN(a5)              ; Sample length in words
move.w  d2,AUD0PER(a5)              ; Period (pitch)
move.w  #64,AUD0VOL(a5)             ; Volume
move.w  #$8001,DMACON(a5)           ; Enable audio DMA

; COPPER (Display Processor)
; --------------------------
; Used for: zone colours, sprite pointers
            dc.w    $2c07,$fffe     ; Wait for line $2c
            dc.w    COLOR00,COLOUR_HOME ; Set background colour

Code Statistics

The complete Phase 1 code:

~3,600 bytes of code
~10,240 bytes of screen buffer
11 letter glyphs
10 digit glyphs
10 cars
5 home zones
3 sound effects
3 life icons
1 frog sprite

All fitting comfortably in the Amiga’s memory.

Systems Review

Movement System

Grid-based positioning
Smooth animation between cells
8-frame hop animation
Joystick edge detection

Collision System

Bounding box detection
Car-frog overlap checking
Road row filtering
Home zone validation

Scoring System

Points for reaching home
Time bonus (remaining seconds × 2)
Level completion bonus
6-digit display

Timer System

Frame-based countdown (3000 = 60 seconds)
Displays in seconds
Triggers death on timeout
Resets per attempt

Level System

Speed scaling per level
Base speeds preserved
Capped at level 8
Endless play beyond

State System

Title screen state
Playing state
Game over state
Fire button transitions

Here’s a summary of the key constants and structures:

; Phase 1 Game Systems Summary
; ============================

; Movement System
; ---------------
; Grid-based: frog moves in discrete 16x16 pixel cells
; Animation: 8 frames @ 2 pixels/frame = smooth hop
frog_grid_x:    dc.w    9           ; Grid position
frog_pixel_x:   dc.w    0           ; Pixel position (for animation)
HOP_FRAMES      equ 8
PIXELS_PER_FRAME equ 2

; State Machine
; -------------
; Frog states control animation behaviour
STATE_IDLE      equ 0               ; Waiting for input
STATE_HOPPING   equ 1               ; Mid-hop animation
STATE_DYING     equ 2               ; Death flash
STATE_GAMEOVER  equ 3               ; No lives left

; Game states control screen flow
GSTATE_TITLE    equ 0               ; Title screen
GSTATE_PLAYING  equ 1               ; Active gameplay
GSTATE_OVER     equ 2               ; Game over screen

; Collision System
; ----------------
; Bounding box overlap check
; frog_x < car_x+width AND frog_x+width > car_x
; Only checked on road rows (7-11)

; Scoring System
; --------------
; 50 points per home reached
; Time bonus: remaining_seconds * 2
; Level bonus: 100 points per level

; Timer System
; ------------
; 3000 frames = 60 seconds at 50Hz PAL
; Counts down each frame, triggers death at 0
TIMER_START     equ 3000

And the complete game flow:

; Phase 1 Complete Game Flow
; ==========================

; Startup
; -------
start:
            lea     CUSTOM,a5
            move.w  #$7fff,DMACON(a5)       ; Disable all DMA
            bsr     clear_screen
            ; ... setup bitplane, sprites, copper ...
            move.w  #$87e1,DMACON(a5)       ; Enable DMA
            move.w  #GSTATE_TITLE,game_state
            bsr     show_title

; Main Loop
; ---------
mainloop:
            bsr     wait_vblank

            ; Dispatch based on game state
            move.w  game_state,d0
            cmp.w   #GSTATE_TITLE,d0
            beq     title_loop              ; Wait for fire
            cmp.w   #GSTATE_OVER,d0
            beq     gameover_loop           ; Wait for fire

            ; PLAYING state
            bsr     update_frog
            bsr     update_timer
            bsr     erase_all_cars
            bsr     move_all_cars
            bsr     draw_all_cars
            bsr     check_home
            bsr     check_collision
            bra     mainloop

; State Transitions
; -----------------
; TITLE -> PLAYING: fire button
; PLAYING -> OVER: last life lost
; OVER -> TITLE: fire button

The Complete Code

;==============================================================================
; SIGNAL - A Frogger-style game for the Commodore Amiga
; Unit 16: Phase 1 Complete
;
; The complete roads-only Frogger. Hardware sprite frog, Blitter cars,
; collision detection, lives, scoring, timer, level progression, and game flow.
; Phase 2 will add the river section with logs, turtles, and crocodiles.
;==============================================================================

;==============================================================================
; 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.asm

What’s Next: Phase 2

Phase 1 gave you the roads. Phase 2 adds the river.

The river section introduces new challenges:

Logs (Units 17-20)

Shaped BOBs with cookie-cut Blitter
The frog rides on logs
Different speeds and sizes

Turtles (Units 21-24)

Animated sprites
Diving behaviour
Timing challenges

Crocodiles (Units 25-28)

Dangerous heads
Safe bodies
Risk/reward gameplay

Bonus Items (Units 29-32)

Flies on logs
Lady frogs
Score multipliers

Phase 2’s key technique is the cookie-cut Blitter mode. Unlike Phase 1’s simple rectangle fills, cookie-cut allows irregular shapes:

; Cookie-cut: D = (A AND C) OR (NOT A AND B)
; A = mask, B = background, C = source, D = destination
move.w  #$0fca,BLTCON0(a5)

This lets us draw shaped logs that preserve the background around their edges—essential for the river’s flowing water effect.

Congratulations

You built a real Amiga game.

From an empty screen to a complete game with:

Hardware sprites
Blitter graphics
Sound effects
Scoring
Lives
Timer
Levels
Game flow

Sixteen units. One playable game. Phase 1 complete.

Phase 2 awaits. The river calls.

What Changed

Unit 15 → Unit 16

+4-3

1	1		`;==============================================================================`
2	2		`; SIGNAL - A Frogger-style game for the Commodore Amiga`
3		-	`; Unit 15: Game States`
	3	+	`; Unit 16: Phase 1 Complete`
4	4		`;`
5		-	`; A complete game needs proper flow: title screen, gameplay, game over.`
6		-	`; This unit adds a state machine that manages these transitions.`
	5	+	`; The complete roads-only Frogger. Hardware sprite frog, Blitter cars,`
	6	+	`; collision detection, lives, scoring, timer, level progression, and game flow.`
	7	+	`; Phase 2 will add the river section with logs, turtles, and crocodiles.`
7	8		`;==============================================================================`
8	9
9	10		`;==============================================================================`