This puzzle game is really vexing, I've tried several times but still can't finish it.

vexing 是动词 vex 的现在分词形式。vex 的意思是"使烦恼、使恼火"，表示让人感到困扰或烦躁。vexing 在这里作为形容词使用，描述"令人烦恼的"状态。