i have a layout much like - https://flexbox.webflow.com/#sidebar
however, when i go to mobile, the left hand side basically goes away. what i'd like is exactly how things are working in the webflow ebooks - https://ebooks.webflow.com/ebook/web-design-101 - when switching to a mobile view, the left hand sidebar then moves to the top.
how is this done? i've been fiddling around for awhile, and am totally clueless. any help would be great. thanks!