A C64 Game - Step 96 | GameDev.net

And a nice little update, Richard Bayliss added sounds effects. Now there's a SFX mode, toggle in the title screen with left/right.

The effects are integrated in the player code as separate "songs". So we add a variable SFX_MODE and check it's value when we want to play an effect or start the music:

No music in title when SFX mode enabled:

          ;initialise music player 
          ldx #0 
          ldy #0 
          lda SFX_MODE 
          bne + 
          
          lda #MUSIC_TITLE_TUNE 
          jsr MUSIC_PLAYER

Play an effect is similar:

          lda SFX_MODE 
          beq + 
          
          lda #MUSIC_PICKUP 
          jsr MUSIC_PLAYER
          
+

To toggle sfx mode move the joystick left/right in the title screen and display its state:

          ;switch through music/sfx mode 
          lda #$04 
          bit JOYSTICK_PORT_II 
          bne .NotLeftPressed 
          
          lda LEFT_RELEASED 
          beq .LeftPressed 
          
          lda SFX_MODE 
          eor #$01 
          sta SFX_MODE 
          jsr DisplaySfxMode 
          
          lda SFX_MODE 
          beq + 
          
          lda #MUSIC_PICKUP 
          jmp ++
          
+ 
          lda #MUSIC_TITLE_TUNE
++ 
          jsr MUSIC_PLAYER 
          lda #0 
          jmp .LeftPressed
          
.NotLeftPressed 
          lda #1
          
.LeftPressed 
          sta LEFT_RELEASED 
          lda #$08 
          bit JOYSTICK_PORT_II 
          bne .NotRightPressed 
          
          lda RIGHT_RELEASED 
          beq .RightPressed 
          
          lda SFX_MODE 
          eor #$01 
          sta SFX_MODE 
          jsr DisplaySfxMode 
          
          lda SFX_MODE 
          beq + 
          
          lda #MUSIC_PICKUP 
          jmp ++
          
+ 
          lda #MUSIC_TITLE_TUNE
++ 
          jsr MUSIC_PLAYER 
          lda #0 
          jmp .RightPressed
          
.NotRightPressed 
          lda #1
          
.RightPressed 
          sta RIGHT_RELEASED 
          
!zone DisplaySfxMode
DisplaySfxMode 
          lda SFX_MODE 
          bne + 
          
          lda #TEXT_MUSIC 
          jmp .DisplaySfxMode
          
+ 
          lda #TEXT_SFX
          
.DisplaySfxMode 
          sta ZEROPAGE_POINTER_1 + 1 
          lda #34 
          sta PARAM1 
          lda #24 
          sta PARAM2 
          jmp DisplayText

Due to technical limitations in the player code there are not too many sounds, but there are enough to make it worthwile.

step96.zip

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