To see it in action, try visiting https://web.archive.org/web/20221014064337/https://en.karelkremel.com/do-you-remember-ultima-online/
(Clickable link is below in a comment)
Do you see the black box quickly shrinking into the upper right hand corner?
It reminds me of DHTML effects of the early 2000's.
I wonder why it was added?