儿戏

You can now stop this kind of bored, naive playgame.

此无聊幼稚儿戏，可以休矣。

You shouldn't toy with great issues.

你不该拿重大问题当儿戏。

You can't play around with this assignment; it's something that needs to be buckled down to seriously.

这次的任务可不是儿戏, 需要认去干。