title: CSS-only Acrylic Material from Fluent Design System
body: <p>With the advent of Microsoft's <a href="http://fluent.microsoft.com/" rel="nofollow noreferrer">Fluent Design System</a> and the propagation of the new Acrylic Material around the Windows ecosystem, I thought it would be great to use it in some Web layouts.</p>
  <p><strong>Acoording to <a href="https://docs.microsoft.com/windows/uwp/style/acrylic" rel="nofollow noreferrer">the spec</a>, the composition of an acrylic layer is:</strong></p>
  <p><a href="https://i.stack.imgur.com/Xlfx5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Xlfx5.png" alt="Image" /></a></p>
  <p>So I went to try a CSS-only approach inspired by the layers in that picture, this way:</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="false" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>body {
    margin: 0;
    font: 1em/1.4 Sans-serif;
    background: url("https://cdn.pixabay.com/photo/2017/03/27/16/50/beach-2179624_1280.jpg") center center;
    background-size: 100vw auto;
  }
  
  main {
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100vh;
  }
  
  .acrylic {
    padding: 4em 6em;
    position: relative;
    overflow: hidden;
  }
  
  .acrylic::before {
    background: url("https://cdn.pixabay.com/photo/2017/03/27/16/50/beach-2179624_1280.jpg") center center;
    background-size: 100vw auto;
    filter: blur(10px);
    content: "";
    position: absolute;
    left: -10px;
    top: -10px;
    width: calc(100% + 20px);
    height: calc(100% + 20px);
    z-index: -1;
  }
  
  .acrylic::after {
    content: "";
    position: absolute;
    left: 0;
    top: 0;
    right: 0;
    bottom: 0;
    z-index: -1;
    opacity: 0.65;
    border: 1px solid #fff;
    background: #fff;
    background-image: url(data:image/png;base64,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);
  }
  
  .shadow {
    border-radius: 1px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1), 0 1px 8px rgba(0, 0, 0, 0.2);
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;main&gt;
    &lt;div class="acrylic shadow"&gt;
      Acrylic material!
    &lt;/div&gt;
  &lt;/main&gt;</code></pre>
  </div>
  </div>
  </p>
  <p>The result is really close to the spec and is also responsive, but has a big problem: just stack another <code>.acrylic</code> div and the background trick doesn't work anymore.</p>
  <p><strong>The question is:</strong> <em>is there some smarter way to gaussian blur without duplicating the body background for each children? Or maybe some smarter way to dinamically calculate its position?</em></p>
  <hr />
  <p><strong>2022 Update</strong></p>
  <p>When I originally posted this question, the <code>backdrop-filter</code> CSS feature was an experimental thing not enabled even in Chrome, so I was asking for an alternative solution, if possible, at the time.</p>
  <p>Time passes... <strong>Finally it's enabled by default on all browsers over 0.5% users.</strong> So <a href="https://stackoverflow.com/a/57417852/424498">it's really simplier to solve nowadays</a> than it was before.</p>