里氏替换原则是面向对象编程中的一个基本概念，它指出子类的对象应该能够替换超类的对象而不影响程序的正确性。

永远看看你还剩下什么。永远不要看你失去了什么。

I’ve always thought that the schoolboy who’s a bit of a troublemaker is the one who’s going to come out and do something really interesting.

The future belongs to those who are willing to challenge the status quo.

事实是，我们都是自己思想的囚徒。