1. Extreme programming is a lightweight and dexterous software development method; at the same time, it is also a very rigorous and thoughtful method. Its foundations and values are communication, simplicity, feedback, and courage; that is, any software project can be improved in four ways: strengthening communication; starting with simplicity; seeking feedback; and being realistic. XP is a near-spiral development method, which decomposes the complex development process into relatively simple small cycles; through active communication, feedback and a series of other methods, developers and customers can be very clear about the development progress , changes, unsolved problems and potential difficulties, etc., and adjust the development process in a timely manner according to the actual situation.