A classic example here is collapsing play and pause onto the same button on an audio player, where it contains the universal play triangle icon until you click it, and then it contains the universal pause icon of two vertical bars.

• 播放和暂停被放在了一个按钮上，播放用标准三角形图标显示，单击之后变成了标准的两道竖条的暂停图标。