Before anyone goes and implement the whole thing, I'll point out that with the release of Moodle 3.7 in a few months, the MoodleCloud theme is about to go through a lot of changes, so the CSS given in there will probably need a significant refactoring.
The techniques used in this tutorial will still work and, for those wanting to take advantage of this right away, using the Boost theme might be easier and more forward-compatible.
Mathieu