   url("large-balloons.jpg")
        );
        background-image: image-set(
          url("large-balloons.avif") type("image/avif"),
          url("large-balloons.jpg") type("image/jpeg")
        );
      }
    </style>
  </head>

  <body>
    <section class="preview">
      <div class="box"></div>
    </section>

    <textarea class="playable playable-css" style="height: 155px">
.box {
  background-image: -webkit-image-set(
    url("large-balloons.avif"),
    url("large-balloons.jpg"));
  background-image