How can I limit the clickable area for a button?

Currently, I'm handling screen taps to start gameplay. I also have a button at the bottom of the screen to toggle sound. Unfortunately, this logic only works partially. Currently, tapping the screen mutes the sound, but the game doesn't start. What adjustments should I make to the script for the game to function correctly?

if event is InputEventMouseButton:
      if event.button_index == MOUSE_BUTTON_LEFT and event.pressed:
        if $TextureButton.pressed:
          if $TextureButton.pressed:
            AudioServer.set_bus_mute(audio_bus_index,not AudioServer.is_bus_mute(audio_bus_index))      

            $Bird.flying = false
        else:
          $Bird.flying = true
          if game_running == false:
            start_game()

If it helps, I used a YouTube tutorial - "". Thanks in advance!