<div class="controls">
<select id="writingMode">
  <option value="horizontal-tb">horizontal-tb</option>
  <option value="vertical-lr">vertical-lr</option>
  <option value="vertical-rl">vertical-rl</option>
</select>
</div>

<div id="container">
<div class="grid">
  <div>Alfa</div>
  <div>Beta</div>
  <div>Charlie</div>
  <div>Delta</div>
  <div>Echo</div>
  <div>Foxtrot</div>
</div>
</div>

* { box-sizing: border-box; }

html {
  font: 1.2em Helvetica, sans-serif;
}

body {
  padding: 40px;
  background-color: #fff;
  color: rgb(108,91,123);
}

.controls {
  background-color: rgba(0,0,0,.1);
  padding: 10px;
  border-radius: .5em;
  border: 1px solid rgba(0,0,0,.2);
  margin: 0 0 2em 0
}

.controls select {
  font-size: .9em;
}

#container {
  writing-mode: horizontal-tb;
}

.grid {
  display: grid;
  grid-gap: 10px;
  grid-template-columns: 5em 5em 5em;
  justify-content: start;
}

.grid :first-child {
  grid-area: 1 / 2 / 3 / 4;
}

.fixed-width {
  width: 200px;
}

.grid > * {
  border: 5px solid rgb(108,91,123);
  border-radius: 5px;
  padding: 10px;
}

var writingMode = document.getElementById("writingMode");
writingMode.addEventListener("change", function (evt) {
  document.getElementById("container").style.writingMode = evt.target.value;
});