Nicely done!
I just thought I’d mention that when viewed in Firefox, Edge and Internet Explorer 11 (at least on my PC), your fade-in effect appears to have something of an issue when the page is scrolled quickly, where instead of each timeline div fading into view, they flicker/flash into view prior to fading in. And this doesn’t seem to happen in Chrome.
I wish I had a better suggestion as to a solution (I’m just learning the ropes myself), but what appears to be happening is that when you scroll down quickly, each div momentarily appears with an opacity value of 1 instead of 0, before being set back to 0, then fading up to 1 again.
Unwelcome news, no doubt! (But it hope it helps.)
Denis