docs: function getPair(index, layer) {
    const pairIndex = index % 2 ? index - 1 : index + 1; // if odd return the index before it, else if even return the index after it
    if (pairIndex < layer.length) {
      return layer[pairIndex];
    }
    return null; // this happens when the given index is the last element in a layer with odd number of elements
  }