html, body {
  margin: 0;
  padding: 0;
  width: 100vw;
  height: 100vh;
}

body {
  background-image: url('../pics/lamb.gif');
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
  background-attachment: fixed;
}

.back {
      position: fixed;
      top: 20px;
      left: 20px;
      z-index: 99999; 
      color: #000000; 
      text-decoration: none;
      font-family: ms gothic;
      font-size: 1rem;
      font-weight: bold;
  
    }
    
    .back:hover {
      color: #ff0000;
    }