.container {
  max-width: 960px;
  height: 100%;
  margin: 0 auto;
  padding: 20px;
  }


.alt-text {
  text-align: center;
  display: block;
  position: relative;
  margin: 20px;
  color: #fff;
  }

figcaption {
  position: absolute;
  opacity: 0;
  left: 0;
  right: 0;
  bottom: 0;
  margin: 0;
  padding: 15px;
  font-size: 14px;
  line-height: 22px;
  background-color: rgba(0,0,0,0.8);
  }

.alt-text:hover > figcaption.alt {
  opacity: 1;
  }