negative-z-index.html | Explore in Territory

<!DOCTYPE html>
<html>
<head>
  <style type="text/css" media="screen">
    .box {
      height: 100px;
      width: 100px;
      background-color: blue;
    }
    .container {
      position: absolute;
      margin: 10px;
      left: 0;
      top: 0;
      z-index: -1;
      background-color: red;
    }

    .compositing {
      will-change: transform;
    }

    .foreground {
      background-color: green;
    }
  </style>
</head>

<body>

  <div class="container box">
    <div class="compositing">
      <div class="foreground box"></div>
    </div>
  </div>

</body>
</html>

chromium/third_party/blink/web_tests/compositing/z-order/negative-z-index.html