<main>
  <fieldset class="radio-controls">
    <legend>position-area:</legend>

    <h3>Default value</h3>
    <label><input type="radio" name="position-area" value="none"> none</label>

    <h3>Two keywords defining a single specific tile</h3>
    <label><input type="radio" name="position-area" value="top left" checked> top left</label>
    <label><input type="radio" name="position-area" value="start end"> start end</label>
    <label><input type="radio" name="position-area" value="block-start center"> block-start center</label>
    <label><input type="radio" name="position-area" value="inline-start block-end"> inline-start block-end</label>
    <label><input type="radio" name="position-area" value="x-start y-end"> x-start y-end</label>
    <label><input type="radio" name="position-area" value="center y-self-end"> center y-self-end</label>

    <h3>Two keywords spanning two tiles</h3>
    <label><input type="radio" name="position-area" value="top span-left"> top span-left</label>
    <label><input type="radio" name="position-area" value="center span-start"> center span-start</label>
    <label><input type="radio" name="position-area" value="inline-start span-block-end"> inline-start span-block-end</label>
    <label><input type="radio" name="position-area" value="y-start span-x-end"> y-start span-x-end</label>

    <h3>Two keywords spanning three tiles</h3>
    <label><input type="radio" name="position-area" value="top span-all"> top span-all</label>
    <label><input type="radio" name="position-area" value="block-end span-all"> block-end span-all</label>
    <label><input type="radio" name="position-area" value="x-self-start span-all"> x-self-start span-all</label>

    <h3>One keyword with implicit second keyword</h3>
    <label><input type="radio" name="position-area" value="top"> top</label>
    <label><input type="radio" name="position-area" value="inline-start"> inline-start</label>
    <label><input type="radio" name="position-area" value="center"> center</label>
    <label><input type="radio" name="position-area" value="span-all"> span-all</label>
    <label><input type="radio" name="position-area" value="end"> end</label>

    <h3>Global values</h3>
    <label><input type="radio" name="position-area" value="inherit"> inherit</label>
    <label><input type="radio" name="position-area" value="initial"> initial</label>
    <label><input type="radio" name="position-area" value="revert"> revert</label>
    <label><input type="radio" name="position-area" value="revert-layer"> revert-layer</label>
    <label><input type="radio" name="position-area" value="unset"> unset</label>
  </fieldset>

  <div class="select-controls">
    <label for="position-area-select">position-area:</label>
    <select name="position-area" id="position-area-select">
      <optgroup label="Default value">
        <option value="none">none</option>
      </optgroup>

      <optgroup label="Two keywords defining a single specific tile">
        <option value="top left" selected>top left</option>
        <option value="start end">start end</option>
        <option value="block-start center">block-start center</option>
        <option value="inline-start block-end">inline-start block-end</option>
        <option value="x-start y-end">x-start y-end</option>
        <option value="center y-self-end">center y-self-end</option>
      </optgroup>

      <optgroup label="Two keywords spanning two tiles">
        <option value="top span-left">top span-left</option>
        <option value="center span-start">center span-start</option>
        <option value="inline-start span-block-end">inline-start span-block-end</option>
        <option value="y-start span-x-end">y-start span-x-end</option>
      </optgroup>

      <optgroup label="Two keywords spanning three tiles">
        <option value="top span-all">top span-all</option>
        <option value="block-end span-all">block-end span-all</option>
        <option value="x-self-start span-all">x-self-start span-all</option>
      </optgroup>

      <optgroup label="One keyword with implicit second keyword">
        <option value="top">top</option>
        <option value="inline-start">inline-start</option>
        <option value="center">center</option>
        <option value="span-all">span-all</option>
        <option value="end">end</option>
      </optgroup>

      <optgroup label="Global values">
        <option value="inherit">inherit</option>
        <option value="initial">initial</option>
        <option value="revert">revert</option>
        <option value="revert-layer">revert-layer</option>
        <option value="unset">unset</option>
      </optgroup>
    </select>
  </div>
  <div class="grid">
    <div class="anchor">
      <svg viewBox="0 0 256 256"><rect width="256" height="256" fill="none"/><line x1="128" y1="232" x2="128" y2="80" fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="16"/><circle cx="128" cy="56" r="24" fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="16"/><line x1="88" y1="120" x2="168" y2="120" fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="16"/><path d="M216,144c0,64-88,24-88,88,0-64-88-24-88-88" fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="16"/></svg>
    </div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
  </div>
  <div class="tooltip">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
  </div>
</main>
<style>
  main {
    padding: 2rem;
    display: grid;
    grid-template-columns: 300px 1fr;
    gap: 2rem;
    align-items: center;
  }
  .radio-controls {
    margin-bottom: 1rem;
    border: 1px solid lightgray;
    padding: 1rem;
  }

  .radio-controls h3 {
    margin: 1rem 0 0.5rem 0;
    font-size: 0.9rem;
    color: #666;
  }

  .radio-controls h3:first-of-type {
    margin-top: 0;
  }

  .radio-controls label {
    display: block;
    margin: 0.25rem 0;
    cursor: pointer;
  }

  .select-controls {
    margin-bottom: 1rem;
    display: none;
  }

  .select-controls label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: bold;
  }

  .select-controls select {
    font-size: 1rem;
    padding: 0.5rem;
    width: 100%;
  }

  @media (max-width: 800px) {
    main {
      grid-template-columns: 1fr;
      grid-template-rows: auto auto;
    }

    .radio-controls {
      display: none;
    }

    .select-controls {
      display: block;
    }
  }
  .grid {
    display: grid;
    grid-template-columns: 1fr 50px 1fr;
    grid-template-rows: 1fr 50px 1fr;
    grid-template-areas:
      "top-left top-center top-right"
      "center-left center center-right"
      "bottom-left bottom-center bottom-right";
    aspect-ratio: 1 / 1;
    border: 1px solid lightgray;
  }

  .grid > div {
    border: 1px solid lightgray;
  }
  .anchor {
    grid-area: center;
    display: grid;
    place-items: center;
    anchor-name: --anchor;
  }

  .anchor svg {
    width: 50px;
    height: 50px;
    color: darkgray;
  }

  .tooltip {
    position: fixed;
    position-anchor: --anchor;
    position-area: top left;
    padding: 1rem;
    border: 1px solid lightgray;
    border-radius: 0.5rem;
    background-color: black;
    color: white;
  }
</style>
<script>
  const radios = document.querySelectorAll('input[name="position-area"]');
  const tooltip = document.querySelector('.tooltip');

  radios.forEach(radio => {
    radio.addEventListener('change', (e) => {
      tooltip.style.positionArea = e.target.value;
    });
  });

  const select = document.getElementById('position-area-select');
  select.addEventListener('change', (e) => {
    tooltip.style.positionArea = e.target.value;
  });
</script>