Anything that tells him to sense something like the user's mouse or the edge of his screen is actually purple in color; and so they're nicely colorized and all this but the one that's adventurous right now is this.

能够让计算机感知鼠标或屏幕边缘的图块,都是紫色的;,这些图块五颜六色,但这里有一个不太靠谱的按键。

哈佛公开课 - 计算机科学课程节选