body::before {
  position: fixed;
  z-index: -1;
  display: block;
  height: 100%;
  content: "";
  background: #4b4e9f;
  right: 0;
}
@media (min-width: 768px) {
  body::before {
    width: calc((100vw - 960px) / 2 + 200px);
  }
}
@media (min-width: 992px) {
  body::before {
    width: calc((100vw - 960px) / 2 + 200px - 50px);
  }
}
@media (min-width: 1200px) {
  body::before {
    width: calc((100vw - 1170px) / 2 + 200px);
  }
}