CSS mask Property - Playground Example

<!DOCTYPE html><html><head><style type="text/css">/* Basic page layout */
* {
  box-sizing: border-box;
}

body {
  font-family: system-ui, -apple-system, 'Segoe UI', Roboto, Arial, sans-serif;
  background: linear-gradient(135deg, #f0f4ff, #ffffff);
  min-height: 100vh;
  margin: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 40px;
}

.wrap {
  text-align: center;
  width: 360px;
}

h1 {
  font-size: 18px;
  margin: 0 0 16px;
  color: #0b1220;
}

.photo {
  width: 360px;
  height: 240px;
  border-radius: 12px;
  background-image: url('https://images.unsplash.com/photo-1501785888041-af3ef285b470?auto=format&fit=crop&w=1200&q=80');
  background-size: cover;
  background-position: center;
  box-shadow: 0 8px 24px rgba(10, 10, 20, 0.12);

  /* CSS mask: a circular opaque area (black) with transparent outside */
  mask-image: radial-gradient(circle at 50% 40%, black 0%, black 36%, transparent 37%);
  -webkit-mask-image: radial-gradient(circle at 50% 40%, black 0%, black 36%, transparent 37%);
  mask-repeat: no-repeat;
  -webkit-mask-repeat: no-repeat;
  mask-position: center;
  -webkit-mask-position: center;
  mask-size: 70% 70%;
  -webkit-mask-size: 70% 70%;

  /* subtle animated movement of the mask to demonstrate dynamic masking */
  animation: floatMask 6s ease-in-out infinite;
}

@keyframes floatMask {
  0% {
    mask-position: 20% 30%;
    -webkit-mask-position: 20% 30%;
  }

  50% {
    mask-position: 80% 70%;
    -webkit-mask-position: 80% 70%;
  }

  100% {
    mask-position: 20% 30%;
    -webkit-mask-position: 20% 30%;
  }
}

.caption {
  font-size: 13px;
  color: #606680;
  margin-top: 12px;
}</style></head><body><div class="wrap">
  <h1>CSS mask  -  radial spotlight</h1>
  <div class="photo" role="img" aria-label="Scenic photo masked by a circular spotlight"></div>
  <p class="caption">The circle is created with CSS mask (and -webkit-mask for Safari).</p>
</div></body></html>