You've got a loop, you've got a condition and a boolean to check if he's touching the edge, and some statements to tell him to shout or to actually turn around.

我们有一个循环，通过一个条件和一个布尔值来判断,是否触到了边缘，还有一些语句,让它回头并咆哮。

哈佛公开课 - 计算机科学课程节选

Once you know what pieces to look for, what mental constructs to reach for, can you realize all right I want to make some dancing figures go back and forth, I need to loop this way and loop this way and check if I'm on the edge and so forth.

一旦确定需要查找的部分,想要达到那种层次，你是否意识到,我想做出一些可以来回走动跳舞的人，我需要按这种方式那种方式让它转圈,并检查我是否,到了屏幕的边缘等等。

哈佛公开课 - 计算机科学课程节选