Thank you for the comment.
You have to drag cards that sum 13 on top of each other. For example: Q + A, J + 2, 10 + 3, and so on.
The K's value is already 13, that's why it's the only card that can be directly put in that space.
I will add feedbacks to make the rules easier to understand in the next update.
以下是 ChatGPT 对上面文字的翻译：
谢谢你的评论。
你需要把点数加起来等于 13 的牌拖到一起。例如：Q + A、J + 2、10 + 3，依此类推。
K 的点数本身就是 13，所以它是唯一一张可以直接放到那个位置的牌。
我会在下一次更新中加入一些提示，让游戏规则更容易理解