The @mootari’s notebook: Fullscreen Layout Demo / Fabian Iwand | Observable is currently broken. I imagine something has changed recently in the Observable’s DOM.
Thanks for pointing it out! Can you please check the update I just published?
Changes:
- cell divs now have an additional wrapper below
body -
height: 100%on the wrapper would no longer work and needed to be specified as100vh
Thanks ! I fixed my notebook as well: https://observablehq.com/@severo/two-columns-layout-in-fullscreen-mode
I would advise against using float for columns. These days there are far better options, like display:flex and display:grid. Also, at least in my browser, the cell containing the “Side column” headline appear below the videos.
Oh, you’re right, the breakLayoutAtCell parameter was wrong 
For the layout, with my poor CSS skills I couldn’t find a better way of getting what I want, and I had no more luck asking on StackOverflow: CSS layout: how to break the first column after N elements, and follow in the second column, just with CSS? - Stack Overflow.
It can be quite tricky to flow elements across columns without additional wrappers. For what it’s worth: display:inline-block can often be easier to handle.