This lecture platform works by allowing groups of users
create slides and presentation, but at the same time also
define a transcription of it.
It is all done in markdown however, to avoid the
users to fiddle around with styling.
Along with each slide, a speaking script
provided, which is read via TTS (text to speech)
alongside with the slides.
This allows for students to use the lecture, and provide
feedback by pushing suggestion for modifications to the
text to speech script
With a more powerful semantic markup, you could allow
for variable complexity for the slides. Changing the
lecturer from a short summary, to a hyper detailed
explanation at a click of a button.