Game 1 Unit 11 of 64 1 hr learning time

Sound Effects

Paula plays samples. Hop sound. Death sound. Home sound. Audio presence.

17% of Signal

Mark as complete Completed!

What You’re Building

Audio presence.

A silent game feels dead. This unit adds sound effects using Paula, the Amiga’s audio chip. Simple 8-bit waveforms play when you hop, die, or dock at a home zone. The result: immediate audio feedback that makes the game feel alive.

By the end of this unit:

Hop sound when the frog jumps
Death sound when hit by a car
Success sound when reaching home
Understanding of Paula’s sample playback

Unit 11 Screenshot

Paula: The Audio Chip

The Amiga’s Paula chip handles audio output. It has 4 independent channels, each capable of playing 8-bit signed PCM samples at variable rates. For our simple sound effects, we only need one channel.

; Paula Audio Registers
; Channel 0 registers for sound playback

; Paula audio registers (channel 0)
AUD0LC      equ $0a0           ; Sample pointer (long)
AUD0LEN     equ $0a4           ; Sample length in words
AUD0PER     equ $0a6           ; Period (pitch): lower = higher
AUD0VOL     equ $0a8           ; Volume: 0-64

; Audio DMA control
; DMACON bit 0 = AUD0 channel enable
; To disable: move.w #$0001,DMACON(a5)
; To enable:  move.w #$8001,DMACON(a5)

; Period values (approximate):
; 200 = high pitch (chirp)
; 300 = medium pitch
; 500 = low pitch (death)

; Sample format:
; - 8-bit signed values (-128 to +127)
; - $7f = maximum positive, $80 = maximum negative
; - Must be in Chip RAM for DMA access
; - Length in words (bytes / 2)

Paula expects 8-bit signed samples. Values range from -128 ($80) to +127 ($7f). Sample data must reside in Chip RAM so the DMA can access it.

The Play Sound Routine

A single routine handles all sound playback:

; Play Sound Effect
; Select sound by number, configure Paula, trigger playback

; Sound effect numbers
SND_HOP         equ 0
SND_DEATH       equ 1
SND_HOME        equ 2

play_sound:
            ; Get sound data based on D0
            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       ; Length in words
            move.w  #300,d2             ; Period (medium pitch)
            bra.s   .do_play

.play_death:
            lea     sound_death,a0
            move.w  #DEATH_LEN/2,d1
            move.w  #500,d2             ; Period (lower pitch)
            bra.s   .do_play

.play_home:
            lea     sound_home,a0
            move.w  #HOME_LEN/2,d1
            move.w  #200,d2             ; Period (higher pitch)

.do_play:
            ; Stop any playing sound first
            move.w  #$0001,DMACON(a5)   ; Disable AUD0

            ; Configure channel
            move.l  a0,AUD0LC(a5)       ; Sample pointer
            move.w  d1,AUD0LEN(a5)      ; Length in words
            move.w  d2,AUD0PER(a5)      ; Period (pitch)
            move.w  #64,AUD0VOL(a5)     ; Maximum volume

            ; Start playback
            move.w  #$8001,DMACON(a5)   ; Enable AUD0

            rts

Audio DMA

Paula uses DMA to fetch sample data automatically. We enable it in two places:

At startup, include audio DMA in the initial DMACON setup:

move.w  #$87e1,DMACON(a5)   ; Enable Copper, Blitter, Sprites, AUD0

When triggering a sound, we toggle the channel’s DMA:

move.w  #$0001,DMACON(a5)   ; Disable AUD0 (clear bit 0)
; ... set up registers ...
move.w  #$8001,DMACON(a5)   ; Enable AUD0 (set bit 0)

Creating Sound Waveforms

Our sounds are simple square waves defined inline:

; Sound Data - 8-bit Signed Samples
; Simple square waves for game effects

            even

; Hop sound - short square wave burst (32 bytes)
sound_hop:
            dc.b    $7f,$7f,$7f,$7f,$7f,$7f,$7f,$7f     ; High (+127)
            dc.b    $80,$80,$80,$80,$80,$80,$80,$80     ; Low  (-128)
            dc.b    $7f,$7f,$7f,$7f,$7f,$7f,$7f,$7f     ; High
            dc.b    $80,$80,$80,$80,$80,$80,$80,$80     ; Low
HOP_LEN     equ     *-sound_hop

; Death sound - descending tone (variable wavelength)
sound_death:
            dc.b    $7f,$7f,$7f,$7f,$80,$80,$80,$80     ; Fast cycle (high)
            dc.b    $7f,$7f,$7f,$7f,$80,$80,$80,$80
            dc.b    $7f,$7f,$7f,$7f,$7f,$80,$80,$80,$80,$80  ; Slower
            dc.b    $7f,$7f,$7f,$7f,$7f,$7f,$80,$80,$80,$80,$80,$80  ; Even slower
            dc.b    $7f,$7f,$7f,$7f,$7f,$7f,$7f,$7f     ; Slowest (low)
            dc.b    $80,$80,$80,$80,$80,$80,$80,$80
DEATH_LEN   equ     *-sound_death

; Home sound - bright chirp (ascending)
sound_home:
            dc.b    $7f,$80,$7f,$80,$7f,$80,$7f,$80     ; Very fast (high pitch)
            dc.b    $7f,$80,$7f,$80,$7f,$80,$7f,$80
            dc.b    $7f,$7f,$80,$80,$7f,$7f,$80,$80     ; Medium
            dc.b    $7f,$7f,$80,$80,$7f,$7f,$80,$80
            dc.b    $7f,$7f,$7f,$80,$80,$80,$7f,$7f,$7f,$80,$80,$80  ; Lower
            dc.b    $00,$00,$00,$00                     ; Silence
HOME_LEN    equ     *-sound_home

The hop sound is a short burst, the death sound has varying cycle length for a descending effect, and the home sound is a bright chirp.

Triggering Sounds

We call play_sound at the appropriate moments:

On hop start:

.start_hop:
    move.w  #STATE_HOPPING,frog_state
    clr.w   frog_anim_frame

    ; Play hop sound
    move.w  #SND_HOP,d0
    bsr     play_sound

On death:

trigger_death:
    move.w  #STATE_DYING,frog_state
    ; ...

    ; Play death sound
    move.w  #SND_DEATH,d0
    bsr     play_sound

On reaching home:

    ; Home is empty - fill it!
    move.w  #1,0(a0,d1.w)
    add.l   #POINTS_PER_HOME,score

    ; Play success sound
    move.w  #SND_HOME,d0
    bsr     play_sound

Why Stop Before Playing?

We disable the channel before setting new values:

move.w  #$0001,DMACON(a5)   ; Disable AUD0

This ensures clean transitions. If a sound is already playing and we change the sample pointer, we might hear a glitch. Stopping first creates a clean break.

Sound Constants

We define symbolic constants for cleaner code:

SND_HOP         equ 0
SND_DEATH       equ 1
SND_HOME        equ 2

This makes the calling code self-documenting:

move.w  #SND_HOME,d0        ; Clear intent
bsr     play_sound

Key Takeaways

Paula plays 8-bit signed samples via DMA
AUD0LC points to sample data in Chip RAM
AUD0LEN is length in words, not bytes
AUD0PER controls pitch (lower = higher)
AUD0VOL sets volume (0-64)
Audio DMA must be enabled for playback
Stop before play prevents audio glitches
Inline waveforms work for simple effects

The Code

;==============================================================================
; SIGNAL - A Frogger-style game for the Commodore Amiga
; Unit 11: Sound Effects
;
; A game without sound feels lifeless. This unit adds audio feedback using
; Paula, the Amiga's sound chip. Simple 8-bit waveforms play when you hop,
; die, or reach a home zone.
;==============================================================================

;==============================================================================
; 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

; Lives system
START_LIVES     equ 3

; Home zones
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

; 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

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

; Paula audio registers (channel 0)
AUD0LC      equ $0a0           ; Sample pointer (long)
AUD0LEN     equ $0a4           ; Sample length in words
AUD0PER     equ $0a6           ; Period (lower = higher pitch)
AUD0VOL     equ $0a8           ; Volume (0-64)

;==============================================================================
; 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)

            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 (sprite 0 = frog)
            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)

            ; Set up life icon sprites
            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)

            ; Enable DMA (including audio channel 0)
            move.w  #$87e1,DMACON(a5)   ; +AUD0

;==============================================================================
; MAIN LOOP
;==============================================================================

mainloop:
            bsr     wait_vblank

            ; Check game state
            cmp.w   #STATE_GAMEOVER,frog_state
            beq     .game_over_loop

            ; Normal game loop
            bsr     update_frog
            bsr     update_sprite

            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

.game_over_loop:
            btst    #7,$bfe001
            bne.s   mainloop

            ; Restart game
            bsr     init_game
            bsr     update_life_display
            bsr     clear_screen

            bra     mainloop

;==============================================================================
; SOUND ROUTINES
;==============================================================================

;------------------------------------------------------------------------------
; PLAY_SOUND - Play a sound effect
; Input: D0 = sound number (SND_HOP, SND_DEATH, SND_HOME)
;------------------------------------------------------------------------------
play_sound:
            ; Get sound data address and parameters
            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       ; Length in words
            move.w  #300,d2             ; Period (medium pitch)
            bra.s   .do_play

.play_death:
            lea     sound_death,a0
            move.w  #DEATH_LEN/2,d1
            move.w  #500,d2             ; Period (lower pitch)
            bra.s   .do_play

.play_home:
            lea     sound_home,a0
            move.w  #HOME_LEN/2,d1
            move.w  #200,d2             ; Period (higher pitch)

.do_play:
            ; Stop any playing sound first
            move.w  #$0001,DMACON(a5)   ; Disable AUD0

            ; Set sample pointer
            move.l  a0,AUD0LC(a5)

            ; Set length (in words)
            move.w  d1,AUD0LEN(a5)

            ; Set period
            move.w  d2,AUD0PER(a5)

            ; Set volume (max = 64)
            move.w  #64,AUD0VOL(a5)

            ; Enable audio DMA
            move.w  #$8001,DMACON(a5)   ; Enable AUD0

            rts

;==============================================================================
; GAME INITIALISATION
;==============================================================================

init_game:
            move.w  #START_LIVES,lives
            clr.l   score

            lea     home_filled,a0
            moveq   #NUM_HOMES-1,d0
.clear_homes:
            clr.w   (a0)+
            dbf     d0,.clear_homes

            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.s   .not_home
            cmp.w   #HOME_0_X+2,d0
            blt.s   .home_0

            cmp.w   #HOME_1_X,d0
            blt.s   .not_home
            cmp.w   #HOME_1_X+2,d0
            blt.s   .home_1

            cmp.w   #HOME_2_X,d0
            blt.s   .not_home
            cmp.w   #HOME_2_X+2,d0
            blt.s   .home_2

            cmp.w   #HOME_3_X,d0
            blt.s   .not_home
            cmp.w   #HOME_3_X+2,d0
            blt.s   .home_3

            cmp.w   #HOME_4_X,d0
            blt.s   .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

            ; Play success sound
            move.w  #SND_HOME,d0
            bsr     play_sound

            bsr     update_home_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

            lea     home_filled,a0
            moveq   #NUM_HOMES-1,d0
.clear:
            clr.w   (a0)+
            dbf     d0,.clear

            bsr     update_home_display

.not_complete:
            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

            ; Play death sound
            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
            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

            ; Play hop sound
            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

home_filled:    dc.w    0,0,0,0,0

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

;==============================================================================
; 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

;==============================================================================
; SOUND DATA (8-bit signed samples in Chip RAM)
;==============================================================================

            even

; Hop sound - short square wave burst (32 bytes = 16 words)
sound_hop:
            dc.b    $7f,$7f,$7f,$7f,$7f,$7f,$7f,$7f     ; High
            dc.b    $80,$80,$80,$80,$80,$80,$80,$80     ; Low
            dc.b    $7f,$7f,$7f,$7f,$7f,$7f,$7f,$7f     ; High
            dc.b    $80,$80,$80,$80,$80,$80,$80,$80     ; Low
HOP_LEN     equ     *-sound_hop

; Death sound - descending tone (64 bytes = 32 words)
sound_death:
            dc.b    $7f,$7f,$7f,$7f,$80,$80,$80,$80     ; Fast cycle
            dc.b    $7f,$7f,$7f,$7f,$80,$80,$80,$80
            dc.b    $7f,$7f,$7f,$7f,$7f,$80,$80,$80,$80,$80  ; Slower
            dc.b    $7f,$7f,$7f,$7f,$7f,$7f,$80,$80,$80,$80,$80,$80  ; Slower still
            dc.b    $7f,$7f,$7f,$7f,$7f,$7f,$7f,$7f     ; Even slower
            dc.b    $80,$80,$80,$80,$80,$80,$80,$80
DEATH_LEN   equ     *-sound_death

; Home sound - bright chirp (48 bytes = 24 words)
sound_home:
            dc.b    $7f,$80,$7f,$80,$7f,$80,$7f,$80     ; Fast high
            dc.b    $7f,$80,$7f,$80,$7f,$80,$7f,$80
            dc.b    $7f,$7f,$80,$80,$7f,$7f,$80,$80     ; Medium
            dc.b    $7f,$7f,$80,$80,$7f,$7f,$80,$80
            dc.b    $7f,$7f,$7f,$80,$80,$80,$7f,$7f,$7f,$80,$80,$80  ; Lower finish
            dc.b    $00,$00,$00,$00                     ; Silence
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

The game has sound, but no visible score. In Unit 12, we’ll add score display using bitmap fonts—finally showing the player their progress.

What Changed

Unit 10 → Unit 11

+142-98

1	1		`;==============================================================================`
2	2		`; SIGNAL - A Frogger-style game for the Commodore Amiga`
3		-	`; Unit 10: Home Zones`
	3	+	`; Unit 11: Sound Effects`
4	4		`;`
5		-	`; Stakes alone aren't enough—you need a goal. This unit adds 5 home zones at`
6		-	`; the top of the screen. Reach one, it fills in, you respawn. Fill all 5 to`
7		-	`; complete a round. Each successful docking scores 50 points.`
	5	+	`; A game without sound feels lifeless. This unit adds audio feedback using`
	6	+	`; Paula, the Amiga's sound chip. Simple 8-bit waveforms play when you hop,`
	7	+	`; die, or reach a home zone.`
8	8		`;==============================================================================`
9	9
10	10		`;==============================================================================`
			...
50	50
51	51		`; Lives system`
52	52		`START_LIVES equ 3`
53		-	`LIFE_ICON_W equ 1`
54		-	`LIFE_ICON_H equ 8`
55		-	`LIFE_ICON_X equ 8`
56		-	`LIFE_ICON_Y equ 260`
57		-	`LIFE_ICON_SPACING equ 20`
58	53
59	54		`; Home zones`
60	55		`NUM_HOMES equ 5`
61		-	`HOME_ROW equ 0 ; Top row of grid`
	56	+	`HOME_ROW equ 0`
62	57		`POINTS_PER_HOME equ 50`
63	58
64		-	`; Home X positions (grid coordinates): 2, 6, 10, 14, 18`
65		-	`; Each home is 2 cells wide (even column = start of home)`
66	59		`HOME_0_X equ 2`
67	60		`HOME_1_X equ 6`
68	61		`HOME_2_X equ 10`
69	62		`HOME_3_X equ 14`
70	63		`HOME_4_X equ 18`
	64	+
	65	+	`; Audio constants`
	66	+	`SND_HOP equ 0`
	67	+	`SND_DEATH equ 1`
	68	+	`SND_HOME equ 2`
71	69
72	70		`; Colours`
73	71		`COLOUR_BLACK equ $0000`
74	72		`COLOUR_HOME equ $0282`
75	73		`COLOUR_HOME_LIT equ $03a3`
76		-	`COLOUR_HOME_FILLED equ $0f80 ; Orange for filled homes`
	74	+	`COLOUR_HOME_FILLED equ $0f80`
77	75		`COLOUR_WATER1 equ $0148`
78	76		`COLOUR_WATER2 equ $026a`
79	77		`COLOUR_MEDIAN equ $0383`
			...
85	83		`COLOUR_EYES equ $0ff0`
86	84		`COLOUR_OUTLINE equ $0000`
87	85		`COLOUR_CAR equ $0f00`
88		-	`COLOUR_LIFE equ $00f0`
89	86
90	87		`;==============================================================================`
91	88		`; HARDWARE REGISTERS`
			...
123	120		`SPR1PTL equ $126`
124	121		`SPR2PTH equ $128`
125	122		`SPR2PTL equ $12a`
	123	+
	124	+	`; Paula audio registers (channel 0)`
	125	+	`AUD0LC equ $0a0 ; Sample pointer (long)`
	126	+	`AUD0LEN equ $0a4 ; Sample length in words`
	127	+	`AUD0PER equ $0a6 ; Period (lower = higher pitch)`
	128	+	`AUD0VOL equ $0a8 ; Volume (0-64)`
126	129
127	130		`;==============================================================================`
128	131		`; CODE SECTION`
			...
162	165		`lea sprptl_val,a1`
163	166		`move.w d0,(a1)`
164	167
165		-	`; Set up life icon sprites (sprites 1, 2, 3)`
	168	+	`; Set up life icon sprites`
166	169		`bsr setup_life_sprites`
167	170
168	171		`bsr update_sprite`
			...
173	176		`move.l a0,COP1LC(a5)`
174	177		`move.w d0,COPJMP1(a5)`
175	178
176		-	`; Enable DMA`
177		-	`move.w #$87e0,DMACON(a5)`
	179	+	`; Enable DMA (including audio channel 0)`
	180	+	`move.w #$87e1,DMACON(a5) ; +AUD0`
178	181
179	182		`;==============================================================================`
180	183		`; MAIN LOOP`
			...
206	209		`bra mainloop`
207	210
208	211		`.game_over_loop:`
209		-	`; Game over - wait for fire button to restart`
210	212		`btst #7,$bfe001`
211	213		`bne.s mainloop`
212	214
			...
216	218		`bsr clear_screen`
217	219
218	220		`bra mainloop`
	221	+
	222	+	`;==============================================================================`
	223	+	`; SOUND ROUTINES`
	224	+	`;==============================================================================`
	225	+
	226	+	`;------------------------------------------------------------------------------`
	227	+	`; PLAY_SOUND - Play a sound effect`
	228	+	`; Input: D0 = sound number (SND_HOP, SND_DEATH, SND_HOME)`
	229	+	`;------------------------------------------------------------------------------`
	230	+	`play_sound:`
	231	+	`; Get sound data address and parameters`
	232	+	`cmp.w #SND_HOP,d0`
	233	+	`beq.s .play_hop`
	234	+	`cmp.w #SND_DEATH,d0`
	235	+	`beq.s .play_death`
	236	+	`cmp.w #SND_HOME,d0`
	237	+	`beq.s .play_home`
	238	+	`rts`
	239	+
	240	+	`.play_hop:`
	241	+	`lea sound_hop,a0`
	242	+	`move.w #HOP_LEN/2,d1 ; Length in words`
	243	+	`move.w #300,d2 ; Period (medium pitch)`
	244	+	`bra.s .do_play`
	245	+
	246	+	`.play_death:`
	247	+	`lea sound_death,a0`
	248	+	`move.w #DEATH_LEN/2,d1`
	249	+	`move.w #500,d2 ; Period (lower pitch)`
	250	+	`bra.s .do_play`
	251	+
	252	+	`.play_home:`
	253	+	`lea sound_home,a0`
	254	+	`move.w #HOME_LEN/2,d1`
	255	+	`move.w #200,d2 ; Period (higher pitch)`
	256	+
	257	+	`.do_play:`
	258	+	`; Stop any playing sound first`
	259	+	`move.w #$0001,DMACON(a5) ; Disable AUD0`
	260	+
	261	+	`; Set sample pointer`
	262	+	`move.l a0,AUD0LC(a5)`
	263	+
	264	+	`; Set length (in words)`
	265	+	`move.w d1,AUD0LEN(a5)`
	266	+
	267	+	`; Set period`
	268	+	`move.w d2,AUD0PER(a5)`
	269	+
	270	+	`; Set volume (max = 64)`
	271	+	`move.w #64,AUD0VOL(a5)`
	272	+
	273	+	`; Enable audio DMA`
	274	+	`move.w #$8001,DMACON(a5) ; Enable AUD0`
	275	+
	276	+	`rts`
219	277
220	278		`;==============================================================================`
221	279		`; GAME INITIALISATION`
			...
225	283		`move.w #START_LIVES,lives`
226	284		`clr.l score`
227	285
228		-	`; Clear all homes`
229	286		`lea home_filled,a0`
230	287		`moveq #NUM_HOMES-1,d0`
231	288		`.clear_homes:`
			...
240	297		`; HOME ZONE DETECTION`
241	298		`;==============================================================================`
242	299
243		-	`;------------------------------------------------------------------------------`
244		-	`; CHECK_HOME - Check if frog has reached a home zone`
245		-	`;------------------------------------------------------------------------------`
246	300		`check_home:`
247		-	`; Only check if at top row`
248	301		`move.w frog_grid_y,d0`
249	302		`tst.w d0`
250	303		`bne .not_home`
251	304
252		-	`; At top row - determine which home`
253	305		`move.w frog_grid_x,d0`
254	306
255		-	`; Check home 0 (X = 2-3)`
256	307		`cmp.w #HOME_0_X,d0`
257	308		`blt.s .not_home`
258	309		`cmp.w #HOME_0_X+2,d0`
259	310		`blt.s .home_0`
260	311
261		-	`; Check home 1 (X = 6-7)`
262	312		`cmp.w #HOME_1_X,d0`
263	313		`blt.s .not_home`
264	314		`cmp.w #HOME_1_X+2,d0`
265	315		`blt.s .home_1`
266	316
267		-	`; Check home 2 (X = 10-11)`
268	317		`cmp.w #HOME_2_X,d0`
269	318		`blt.s .not_home`
270	319		`cmp.w #HOME_2_X+2,d0`
271	320		`blt.s .home_2`
272	321
273		-	`; Check home 3 (X = 14-15)`
274	322		`cmp.w #HOME_3_X,d0`
275	323		`blt.s .not_home`
276	324		`cmp.w #HOME_3_X+2,d0`
277	325		`blt.s .home_3`
278	326
279		-	`; Check home 4 (X = 18-19)`
280	327		`cmp.w #HOME_4_X,d0`
281	328		`blt.s .not_home`
282	329		`cmp.w #HOME_4_X+2,d0`
283	330		`blt.s .home_4`
284	331
285		-	`; Between homes - death!`
286	332		`bra .death_between`
287	333
288	334		`.home_0: moveq #0,d1`
			...
296	342		`.home_4: moveq #4,d1`
297	343
298	344		`.check_filled:`
299		-	`; D1 = home index (0-4)`
300	345		`lea home_filled,a0`
301		-	`add.w d1,d1 ; *2 for word offset`
	346	+	`add.w d1,d1`
302	347		`tst.w 0(a0,d1.w)`
303		-	`bne.s .death_filled ; Already filled - death!`
	348	+	`bne.s .death_filled`
304	349
305		-	`; Home is empty - fill it!`
306	350		`move.w #1,0(a0,d1.w)`
307		-
308		-	`; Add points`
309	351		`add.l #POINTS_PER_HOME,score`
310	352
311		-	`; Update display`
312		-	`bsr update_home_display`
	353	+	`; Play success sound`
	354	+	`move.w #SND_HOME,d0`
	355	+	`bsr play_sound`
313	356
314		-	`; Check if all homes filled`
	357	+	`bsr update_home_display`
315	358		`bsr check_round_complete`
316		-
317		-	`; Respawn frog`
318	359		`bsr reset_frog`
319	360		`rts`
320	361
321	362		`.death_filled:`
322		-	`; Landed on filled home - death`
323		-	`bsr trigger_death`
324		-	`rts`
325		-
326	363		`.death_between:`
327		-	`; Landed between homes (on lily pad gaps) - death`
328	364		`bsr trigger_death`
329	365		`rts`
330	366
331	367		`.not_home:`
332	368		`rts`
333	369
334		-	`;------------------------------------------------------------------------------`
335		-	`; CHECK_ROUND_COMPLETE - Check if all 5 homes are filled`
336		-	`;------------------------------------------------------------------------------`
337	370		`check_round_complete:`
338	371		`lea home_filled,a0`
339	372		`moveq #NUM_HOMES-1,d0`
340		-	`moveq #0,d1 ; Count filled homes`
	373	+	`moveq #0,d1`
341	374
342	375		`.loop:`
343	376		`tst.w (a0)+`
			...
345	378		`addq.w #1,d1`
346	379		`dbf d0,.loop`
347	380
348		-	`; All homes filled - reset for next round`
349	381		`cmp.w #NUM_HOMES,d1`
350	382		`bne.s .not_complete`
351	383
352		-	`; Clear all homes for next round`
353	384		`lea home_filled,a0`
354	385		`moveq #NUM_HOMES-1,d0`
355	386		`.clear:`
			...
357	388		`dbf d0,.clear`
358	389
359	390		`bsr update_home_display`
360		-	`; Could add bonus points here, increase speed, etc.`
361	391
362	392		`.not_complete:`
363	393		`rts`
364	394
365		-	`;------------------------------------------------------------------------------`
366		-	`; UPDATE_HOME_DISPLAY - Update Copper colours to show filled homes`
367		-	`;------------------------------------------------------------------------------`
368	395		`update_home_display:`
369	396		`lea home_filled,a0`
370	397		`lea home_colour_0,a1`
371	398
372		-	`; Home 0`
373	399		`tst.w (a0)+`
374	400		`beq.s .home0_empty`
375	401		`move.w #COLOUR_HOME_FILLED,(a1)`
			...
419	445		`;==============================================================================`
420	446
421	447		`setup_life_sprites:`
422		-	`; Sprite 1`
423	448		`lea life_icon_1,a0`
424	449		`move.l a0,d0`
425	450		`swap d0`
			...
429	454		`lea spr1ptl_val,a1`
430	455		`move.w d0,(a1)`
431	456
432		-	`; Sprite 2`
433	457		`lea life_icon_2,a0`
434	458		`move.l a0,d0`
435	459		`swap d0`
			...
439	463		`lea spr2ptl_val,a1`
440	464		`move.w d0,(a1)`
441	465
442		-	`; Sprite 3`
443	466		`lea life_icon_3,a0`
444	467		`move.l a0,d0`
445	468		`swap d0`
			...
452	475		`rts`
453	476
454	477		`update_life_display:`
455		-	`; Life 1 (always show if lives >= 1)`
456	478		`lea life_icon_1,a0`
457	479		`move.w lives,d0`
458	480		`cmp.w #1,d0`
			...
531	553		`move.w #DEATH_FRAMES,death_timer`
532	554		`move.w #FLASH_COLOUR,flash_colour`
533	555
534		-	`; Decrement lives`
	556	+	`; Play death sound`
	557	+	`move.w #SND_DEATH,d0`
	558	+	`bsr play_sound`
	559	+
535	560		`subq.w #1,lives`
536	561		`bsr update_life_display`
537	562
			...
644	669		`subq.w #1,death_timer`
645	670		`bgt.s .still_dying`
646	671
647		-	`; Death complete - check for game over`
648	672		`tst.w lives`
649	673		`beq.s .game_over`
650	674
651		-	`; Still have lives - respawn`
652	675		`bsr reset_frog`
653	676		`bra .done`
654	677
			...
705	728		`.start_hop:`
706	729		`move.w #STATE_HOPPING,frog_state`
707	730		`clr.w frog_anim_frame`
	731	+
	732	+	`; Play hop sound`
	733	+	`move.w #SND_HOP,d0`
	734	+	`bsr play_sound`
	735	+
708	736		`bra.s .done`
709	737
710	738		`.hopping:`
			...
858	886		`lives: dc.w 3`
859	887		`score: dc.l 0`
860	888
861		-	`; Home zone state (0 = empty, 1 = filled)`
862	889		`home_filled: dc.w 0,0,0,0,0`
863	890
864	891		`car_data:`
			...
896	923		`dc.w $0180,$0000`
897	924		`dc.w $0182,COLOUR_CAR`
898	925
899		-	`; Sprite 0-1 palette (frog and life icons share this)`
900	926		`dc.w $01a2,COLOUR_FROG`
901	927		`dc.w $01a4,COLOUR_EYES`
902	928		`dc.w $01a6,COLOUR_OUTLINE`
903	929
904		-	`; Sprite 0 pointer (main frog)`
905	930		`dc.w SPR0PTH`
906	931		`sprpth_val: dc.w $0000`
907	932		`dc.w SPR0PTL`
908	933		`sprptl_val: dc.w $0000`
909	934
910		-	`; Sprite 1 pointer (life icon 1)`
911	935		`dc.w SPR1PTH`
912	936		`spr1pth_val: dc.w $0000`
913	937		`dc.w SPR1PTL`
914	938		`spr1ptl_val: dc.w $0000`
915	939
916		-	`; Sprite 2 pointer (life icon 2)`
917	940		`dc.w SPR2PTH`
918	941		`spr2pth_val: dc.w $0000`
919	942		`dc.w SPR2PTL`
920	943		`spr2ptl_val: dc.w $0000`
921	944
922		-	`; Sprite 3 pointer (life icon 3)`
923		-	`dc.w $0126 ; SPR3PTH`
	945	+	`dc.w $0126`
924	946		`spr3pth_val: dc.w $0000`
925		-	`dc.w $012a ; SPR3PTL`
	947	+	`dc.w $012a`
926	948		`spr3ptl_val: dc.w $0000`
927	949
928		-	`; Home zone row - 5 distinct zones for visual feedback`
929		-	`; Each home changes colour when filled`
	950	+	`; Home zone row`
930	951		`dc.w $2c07,$fffe`
931		-	`dc.w COLOR00,COLOUR_HOME ; Gaps between homes`
	952	+	`dc.w COLOR00,COLOUR_HOME`
932	953
933		-	`; Home 0 (columns 2-3, pixels 48+32=80 to 48+48=96)`
934		-	`dc.w $2c4f,$fffe ; Wait for X=79`
	954	+	`dc.w $2c4f,$fffe`
935	955		`dc.w COLOR00`
936	956		`home_colour_0:`
937	957		`dc.w COLOUR_HOME_LIT`
938	958
939		-	`dc.w $2c5f,$fffe ; Wait for X=95`
940		-	`dc.w COLOR00,COLOUR_HOME ; Gap`
	959	+	`dc.w $2c5f,$fffe`
	960	+	`dc.w COLOR00,COLOUR_HOME`
941	961
942		-	`; Home 1 (columns 6-7)`
943		-	`dc.w $2c8f,$fffe ; Wait for X=143`
	962	+	`dc.w $2c8f,$fffe`
944	963		`dc.w COLOR00`
945	964		`home_colour_1:`
946	965		`dc.w COLOUR_HOME_LIT`
947	966
948		-	`dc.w $2c9f,$fffe ; Wait for X=159`
949		-	`dc.w COLOR00,COLOUR_HOME ; Gap`
	967	+	`dc.w $2c9f,$fffe`
	968	+	`dc.w COLOR00,COLOUR_HOME`
950	969
951		-	`; Home 2 (columns 10-11)`
952		-	`dc.w $2ccf,$fffe ; Wait for X=207`
	970	+	`dc.w $2ccf,$fffe`
953	971		`dc.w COLOR00`
954	972		`home_colour_2:`
955	973		`dc.w COLOUR_HOME_LIT`
956	974
957		-	`dc.w $2cdf,$fffe ; Wait for X=223`
958		-	`dc.w COLOR00,COLOUR_HOME ; Gap`
	975	+	`dc.w $2cdf,$fffe`
	976	+	`dc.w COLOR00,COLOUR_HOME`
959	977
960		-	`; Home 3 (columns 14-15) - past X=223, need high bit`
961		-	`dc.w $2d07,$fffe ; Wait for next pixel region`
	978	+	`dc.w $2d07,$fffe`
962	979		`dc.w COLOR00`
963	980		`home_colour_3:`
964	981		`dc.w COLOUR_HOME_LIT`
965	982
966	983		`dc.w $2d17,$fffe`
967		-	`dc.w COLOR00,COLOUR_HOME ; Gap`
	984	+	`dc.w COLOR00,COLOUR_HOME`
968	985
969		-	`; Home 4 (columns 18-19)`
970	986		`dc.w $2d47,$fffe`
971	987		`dc.w COLOR00`
972	988		`home_colour_4:`
973	989		`dc.w COLOUR_HOME_LIT`
974	990
975	991		`dc.w $2d57,$fffe`
976		-	`dc.w COLOR00,COLOUR_HOME ; End`
	992	+	`dc.w COLOR00,COLOUR_HOME`
977	993
978		-	`; Rest of home row - solid colour`
979	994		`dc.w $3407,$fffe`
980	995		`dc.w COLOR00,COLOUR_HOME_LIT`
981	996		`dc.w $3807,$fffe`
982	997		`dc.w COLOR00,COLOUR_HOME`
983	998
984		-	`; Water rows`
985	999		`dc.w $3c07,$fffe`
986	1000		`dc.w COLOR00,COLOUR_WATER1`
987	1001		`dc.w $4c07,$fffe`
			...
993	1007		`dc.w $7c07,$fffe`
994	1008		`dc.w COLOR00,COLOUR_WATER1`
995	1009
996		-	`; Median`
997	1010		`dc.w $8c07,$fffe`
998	1011		`dc.w COLOR00,COLOUR_MEDIAN`
999	1012
1000		-	`; Road rows`
1001	1013		`dc.w $9c07,$fffe`
1002	1014		`dc.w COLOR00,COLOUR_ROAD1`
1003	1015		`dc.w $ac07,$fffe`
			...
1009	1021		`dc.w $dc07,$fffe`
1010	1022		`dc.w COLOR00,COLOUR_ROAD1`
1011	1023
1012		-	`; Start zone`
1013	1024		`dc.w $ec07,$fffe`
1014	1025		`dc.w COLOR00,COLOUR_START`
1015	1026		`dc.w $f407,$fffe`
			...
1064	1075
1065	1076		`dc.w $0000,$0000`
1066	1077
1067		-	`; Life icon sprites (small frog shape, 8 pixels tall)`
1068	1078		`even`
1069	1079		`life_icon_1:`
1070	1080		`dc.w $0000,$0000`
			...
1103	1113		`dc.w $1800,$0000`
1104	1114		`dc.w $0000,$0000`
1105	1115		`dc.w $0000,$0000`
	1116	+
	1117	+	`;==============================================================================`
	1118	+	`; SOUND DATA (8-bit signed samples in Chip RAM)`
	1119	+	`;==============================================================================`
	1120	+
	1121	+	`even`
	1122	+
	1123	+	`; Hop sound - short square wave burst (32 bytes = 16 words)`
	1124	+	`sound_hop:`
	1125	+	`dc.b $7f,$7f,$7f,$7f,$7f,$7f,$7f,$7f ; High`
	1126	+	`dc.b $80,$80,$80,$80,$80,$80,$80,$80 ; Low`
	1127	+	`dc.b $7f,$7f,$7f,$7f,$7f,$7f,$7f,$7f ; High`
	1128	+	`dc.b $80,$80,$80,$80,$80,$80,$80,$80 ; Low`
	1129	+	`HOP_LEN equ *-sound_hop`
	1130	+
	1131	+	`; Death sound - descending tone (64 bytes = 32 words)`
	1132	+	`sound_death:`
	1133	+	`dc.b $7f,$7f,$7f,$7f,$80,$80,$80,$80 ; Fast cycle`
	1134	+	`dc.b $7f,$7f,$7f,$7f,$80,$80,$80,$80`
	1135	+	`dc.b $7f,$7f,$7f,$7f,$7f,$80,$80,$80,$80,$80 ; Slower`
	1136	+	`dc.b $7f,$7f,$7f,$7f,$7f,$7f,$80,$80,$80,$80,$80,$80 ; Slower still`
	1137	+	`dc.b $7f,$7f,$7f,$7f,$7f,$7f,$7f,$7f ; Even slower`
	1138	+	`dc.b $80,$80,$80,$80,$80,$80,$80,$80`
	1139	+	`DEATH_LEN equ *-sound_death`
	1140	+
	1141	+	`; Home sound - bright chirp (48 bytes = 24 words)`
	1142	+	`sound_home:`
	1143	+	`dc.b $7f,$80,$7f,$80,$7f,$80,$7f,$80 ; Fast high`
	1144	+	`dc.b $7f,$80,$7f,$80,$7f,$80,$7f,$80`
	1145	+	`dc.b $7f,$7f,$80,$80,$7f,$7f,$80,$80 ; Medium`
	1146	+	`dc.b $7f,$7f,$80,$80,$7f,$7f,$80,$80`
	1147	+	`dc.b $7f,$7f,$7f,$80,$80,$80,$7f,$7f,$7f,$80,$80,$80 ; Lower finish`
	1148	+	`dc.b $00,$00,$00,$00 ; Silence`
	1149	+	`HOME_LEN equ *-sound_home`
1106	1150
1107	1151		`;==============================================================================`
1108	1152		`; SCREEN BUFFER`