This is kind of neat from a nostalgia standpoint, but I wish there was some kind of "Encyclopedia of Operating System UI," that broke UI features and paradigms down into their smallest units, described their mechanics, and tracked them across different operating systems and versions. Probably with a particular emphasis on defunct systems when there was a lot more diversity and innovation (e.g. the Canon Cat Leap Keys: <a href="https://www.youtube.com/watch?v=o_TlE_U_X3c">https://www.youtube.com/watch?v=o_TlE_U_X3c</a>)