let swappedNode = null;

draggable.on('drag:start', () => {
  SoundFx.Synth.play('up');
});

draggable.on('swappable:swapped', ({swappedElement}) => {
  swappedNode = swappedElement;
  SoundFx.Synth.play('swap');
});

draggable.on('drag:stop', () => {
  if (swappedNode) {
    SoundFx.Synth.play('downGood');
  } else {
    SoundFx.Synth.play('downBad');
  }

  swappedNode = null;
});