.masthead {
  animation: backShake 90s ease-in-out 0s infinite normal forwards;
  /*background-size: 300%;*/
}

@keyframes backShake {
  0% {
    background-position: 0% 0%;
  }
  16% {
    background-position: 100% 100%;
  }
  32% {
    background-position: 50% 0%;
  }
  48% {
    background-position: 0% 100%;
  }
  64% {
    background-position: 100% 0%;
  }
  80% {
    background-position: 50% 100%;
  }
  100% {
    background-position: 0% 0%;
  }
}

.backmove {
  animation: backShake 90s ease-in-out 0s infinite normal forwards;
  /*background-size: 300%;*/
}