<!DOCTYPE html>
<link rel="author" title="Morten Stenshorne" href="mailto:mstensho@chromium.org">

<style>
  .container {
    float: left;
    margin: 10px;
    text-align: center;
    inline-size: fit-content;
  }
  .multicol {
    inline-size: 320px;
    block-size: 120px;
    border: solid;
    background: lightgray;
  }
  .column {
    float: left;
    inline-size: 100px;
    margin-inline-start: 10px;
  }
  .column:first-child {
    margin-inline-start:0;
  }
  .clipper {
    position: relative;
    border-radius: 50px;
    border: 20px solid blue;
    overflow: clip;
    background: red;
  }
  .clipper.part1 {
    block-size: 100px;
    border-block-end: none;
    border-end-start-radius: 0;
    border-end-end-radius: 0;
  }
  .clipper.part2 {
    block-size: 120px;
    border-block-start: none;
    border-block-end: none;
    border-radius: 0;
  }
  .clipper.part3 {
    block-size: 80px;
    border-block-start: none;
    border-start-start-radius: 0;
    border-start-end-radius: 0;
  }
  .child {
    block-size: 300px;
    background: yellow;
  }
</style>

<p>In each figure there should be a yellow box with a rounded blue border around
  it, split into three columns. There should be no red.</p>

<div class="container">
  horizontal-tb:
  <div class="multicol">
    <div class="column">
      <div class="clipper part1">
        <div class="child"></div>
      </div>
    </div>
    <div class="column">
      <div class="clipper part2">
        <div class="child"></div>
      </div>
    </div>
    <div class="column">
      <div class="clipper part3">
        <div class="child"></div>
      </div>
    </div>
  </div>
</div>

<div class="container">
  vertical-rl:
  <div class="multicol" style="writing-mode:vertical-rl;">
    <div class="column">
      <div class="clipper part1">
        <div class="child"></div>
      </div>
    </div>
    <div class="column">
      <div class="clipper part2">
        <div class="child"></div>
      </div>
    </div>
    <div class="column">
      <div class="clipper part3">
        <div class="child"></div>
      </div>
    </div>
  </div>
</div>

<div class="container">
  vertical-lr:
  <div class="multicol" style="writing-mode:vertical-lr;">
    <div class="column">
      <div class="clipper part1">
        <div class="child"></div>
      </div>
    </div>
    <div class="column">
      <div class="clipper part2">
        <div class="child"></div>
      </div>
    </div>
    <div class="column">
      <div class="clipper part3">
        <div class="child"></div>
      </div>
    </div>
  </div>
</div>
