@keyframes changeBackground {
  0% {
    background-image: url('body_bg_01.png');
    background-repeat: repeat-y
  }

  20% {
    background-color: url('body_bg_02.png');
    background-repeat: repeat-y;
  }

  33% {
    background-image: url('body_bg_03.png');
    background-repeat: repeat-y;
  }

  44% {
    background-image: url('body_bg_04.png');
    background-repeat: repeat-y;
  }

  66% {
    background-image: url('body_bg_05.png');
    background-repeat: repeat-y;
  }

  100% {
    background-image: url('body_bg_06.png');
    background-repeat: repeat-y;
  }
}