body {
 background: linear-gradient(45deg, #ebddca, #b6d2dd, #dea4bd, #a581c4);
 background-repeat: repeat;
 background-attachment: scroll;
 background-size: 900% 900%;
 animation: bgAnim 10s ease-in-out infinite alternate;
 justify-content: center;
}

.topnav {
  border-radius: 1px;
  background: white;
  box-shadow: 3px 3px black;
  overflow: hidden;
  width: 800px;
  margin: 22px auto;
  line-height: 2;
  text-align: center;
}

.topnav a {
  text-align: center;
  margin: 22px;
  font-size: 17px;
}

.topnav a.active {
  background-color: black;
}

@keyframes bgAnim {
  0% {background-position: 25% 50%;}
  50% {background-position: 100% 50%;}
  100% {background-position: 0% 50%;}
}