On his head he wore an orange cap, covered with little silver bells.

VOA: special.2009.02.07

I'm going to start with the simplest example and slowly add on bells and whistles and make it more and more complicated.

我会从最简单的例子开始,逐渐增加难度,让问题越来越复杂

耶鲁公开课 - 基础物理课程节选