W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<head>
<style>
#container {
  width: 80%;
  aspect-ratio: 2/1;
  margin: auto;
  border: solid black 2px;
  overflow-x: scroll;
  overflow-y: hidden;
  white-space: nowrap;
  scroll-snap-type: x mandatory;
}

.blue {
  background-color: lightblue;
  height: 95%;
  aspect-ratio: 6/5;
}

.green {
  background-color: lightgreen;
  height: 80%;
  aspect-ratio: 4/5;
}

.blue, .green {
  margin: 2px;
  display: inline-block;
  scroll-snap-align: none end;
  scroll-margin-block-start: 20px;
  writing-mode: vertical-rl;
}
</style>
</head>
<body>

<h3>CSS scroll-margin-block property.</h3>
<p>With the writing-mode property value set to vertical-rl the start of the element in the block direction is changed from top to right, and this also affects the scroll-margin-block-start property.</p>
<p>In this example, snap position is set to start in block direction, which now is on the right side because of the writing-mode value. Scroll-margin-block-start is also on the right side because of writing-mode value. so the element in focus should snap into place with a 20px distance to the top of the container. But instead, because of the writing-mode value, the element in focus is offset by a 20px margin between child element and container on the right side.</p>

<div id="container">
  <div class="blue">Blue</div>
  <div class="green">Green</div>
  <div class="blue">Blue</div>
  <div class="green">Green</div>
  <div class="blue">Blue</div>
  <div class="green">Green</div>
  <div class="blue">Blue</div>
</div>

</body>
</html>