The reason you don't understand vim is that you don't grok vi.

2.7 million people have visited Stack Overflow to learn how to exit a text editor. The most feared tool in computing is also the most elegant. A 50-year-old proof that designing for constraints produces tools that outlast the constraints themselves.

A multibyte fork of the nvi editor for BSD. Contribute to lichray/nvi2 development by creating an account on GitHub.

POSIX specification for the vi text editor

A small vi/ex editor for editing UTF-8 text. Contribute to aligrudi/neatvi development by creating an account on GitHub.

OpenBSD source via CVSweb
vi tutorials.