Danger

Unsolicited redesigns are fraught for many reasons, but the most perilous aspects are (1) the rōnin designer's ignorance of the strategy which animates the product he's redesigning, and (2) his inability to perform meaningful user testing. His experiments might make everything worse, and he wouldn't know. Consequently, this bit of UI fun is not a redesign. This is just a tribute.

Reasoning

For reference, this is the UI as I found it:

My intentions were:

1. Simplify the navigation and get it out of the way of the content

2. Expand the lecture video to command its rightful visual dominance

3. Make the video controls less obtrusive (and no longer cover the captions)

4. Collapse the 3 independent scroll areas to a single scroll area by default

5. Grant the transcript of the lecture the full vertical height of the browser canvas when open, but otherwise get it out of the way

6. De-emphasize comments while making them easier to read and interact with

7. Make things look nice

Concepts

Dark mode first, and with the transcript hidden:

With the transcript open:

Light mode, transcript closed:

Transcript open: