html, body {
  height: 100%;
  width: 100%;
  text-align: center;
}

.background {
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-orient: vertical;
  -webkit-box-direction: normal;
      -ms-flex-direction: column;
          flex-direction: column;
  -webkit-box-pack: center;
      -ms-flex-pack: center;
          justify-content: center;
  background-image: url(https://source.unsplash.com/random);
  background-size: cover;
  background-repeat: no-repeat;
  height: 100%;
}
.app-section {
  display: block;
  border-radius: 3px;
  padding: 10px;
  width: 300px;
  margin: 20px auto;
  background-color: rgba(255,255,255,.5);
  -webkit-backdrop-filter: blur(15px) saturate(200%);
          backdrop-filter: blur(15px) saturate(200%);
}

#unit {
  background-color: white;
  border-radius: 2px;
  padding: 2px;
  box-shadow: 1px 2px 1px rgba(0,0,0,.5);
}