Appearance of navigation when scrolling up?

Question

css

How can I make the .logo pop back when the screen size is up to 769px when scrolling up? Approximately how it is implemented in this plugin - wicky.nillia.ms/headroom.js, let it be even simpler - so that the .logo leaves the usual way up the page with all the content, and then appears up with any scroll. Those. I need only one event - appearance when scrolling up.
I am unable to connect it. If it can be done without it, it would be more desirable. I can't figure out how to define the Scroll Up event in JS...
codepen.io/dhatt/pen/mAOPEX

Answer 1

1) stackoverflow
2) About the onscroll event here