.csswg.org/css-break/#breaking-rules">

  <style>
  .outer {
    column-count: 1;
    column-rule: 6px solid black;
  }
  .inner {
    column-count: 2;
    column-rule: 3px solid green;
    background-color: lightgreen;
  }
  .block1 {
    background-color: yellow;
    height: 3in;
  }
  .spanner {
    column-span: all;
    height: 2in;
    background-color: lightblue;
  }
  .block2 {
    background-color: pink;
    height: 3in
  }
  </style>

  <article class="outer">
    <article class="inner">
      <div