_prepareCardsForStartingHand() {
    this.showHandLayer();

    // ensure card is added
    const cardNodes = this.getCardNodes();
    const numCards = CONFIG.STARTING_HAND_SIZE;
    for (let i = 0; i < numCards; i++) {
      const cardNode = cardNodes[i];
      if (!cardNode.isRunning()) {
        this._handLayer.addChild(cardNode, 1);
      }
    }

    this._updateCardsLayoutForStartingHand();
  }
Helper function to make sure all card nodes are added to the hand layer and positioned on screen.