pure CSS multiple stacked position sticky?

Question

Is it possible to have multiple sticky elements stacked on top of each other in pure CSS?

The desired behavior can be seen here: https://webthemez.com/demo/sticky-multi-header-scroll/index.html

Only I'd prefer to use pure CSS, instead of a Javascript implementation. I've experimented a bit with multiple sticky elements, but I can't keep them from pushing out other sticky elements. I've tried placing them in the same stacking context:

#sticky .sticky-1,
#sticky .sticky-2
{
  position: sticky;
}
#sticky .sticky-1
{
  top: 1em;
  z-index: 1;
}
#sticky .sticky-2
{
  top: 2em;
  z-index: 1;
}

But can't get it to work, as you can see in below . Any insights would be greatly appreciated!

#container
{
  display: grid;
  grid-template-columns: 50% 50%;
}
#sticky .sticky-1,
#sticky .sticky-2
{
  position: sticky;
}
#sticky .sticky-1
{
  top: 1em;
  z-index: 1;
}
#sticky .sticky-2
{
  top: 2em;
  z-index: 1;
}
#fixed
{
  position: relative;
}
#fixed .sticky-1
{
  position: fixed;
  top: 0;
}
#fixed .sticky-2
{
  position: fixed;
  top: 1em;
}

<div id="container">
<article id="sticky">
  <header>
  
  </header>
  <main><h1 class="sticky-1">Sticky heading</h1>
  <p>here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. Some copy goes here. </p>
    </main>
    <section>
  <h2 class="sticky-2">Both headings should stick at the same time.</h2>
  <p> And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally a little more copy. And finally

Answer 1

You need to make all the elements to stick to the same container (containing block) by adding some offsets.

Here is a basic example where the elements will stick to the body:

body {
  margin:0;
  min-height:200vh;
  border:2px solid;
}
.first {
  height:50px;
  background:red;
  position:sticky;
  top:0;
}

.second {
  height:50px;
  background:blue;
  position:sticky;
  top:52px;
}
.third {
  height:50px;
  background:green;
  position:sticky;
  top:104px;
}

<div class="first"></div>
<p>lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum</p>
<div class="second"></div>
<p>lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum</p>
<div class="third"></div>
<p>lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum</p>