If I type 4 and hit Enter the 4 moves down and the blank space essentially moves up.

如果我键入4并回车，那么4会向下移动,空白区将会上移。

哈佛公开课 - 计算机科学课程节选

Figure out how you can make it move a little to the left, a little to the right, up and down and then repeat in some kind of looping structure.

就是找出办法让它向左移动一小步，向右移动一小步，向上一小步，向下一小步,像这样不断重复。

哈佛公开课 - 计算机科学课程节选