Updated hide / show navbar behavior. I like this better than the last, it's a bit more smooth, hides the new post button too!

For math, it's using 75% of viewport height as the threshold before showing the navs on swiping up. This is to help with sliding too often when you want to preview some things you missed. A better method might be to measure swipe velocity instead. Slow swipe = no show. Fast swip = show bars.