body {
  margin: 0;
  overflow-x: hidden;
}

.menu {
  position: fixed;
  box-sizing: border-box;
  width: 400px;
  height: 100%;
  top: 0;
  margin: 0;
  padding: 20px 40px;
  background-color: #333;
  overflow: auto;
  box-shadow: 0 0 10px #000;
  z-index: 1;
}

.menu__item {
  padding: 10px 0;
  border-top: 1px solid #000;
}

.menu__item:first-child {
  padding-top: 0;
  border-top: none;
}

.menu__item > a {
  color: #fff;
  font-weight: bold;
  font-size: 2em;
}

.body {
  position: relative;
}

.header {
  position: fixed;
  width: 100%;
  top: 0;
  background-color: #fff;
  padding: 10px 40px;
}

.burger {
  position: relative;
  box-sizing: border-box;
  border-color: #007edf;
  border-style: solid;
  border-width: 6px 0;
  background-color: transparent;
  width: 32px;
  height: 32px;
}

.burger:after {
  content: '';
  position: absolute;
  width: 100%;
  height: 6px;
  left: 0;
  top: 7px;
  background-color: #007edf;
}

.content {
  padding: 20px 40px;
  margin-top: 52px;
}

.overlay {
  position: fixed;
  background-color: #000;
  top: 52px;
  left: 0;
  right: 0;
}

/* Define animations and start positions. */
.menu {
  transition: left 400ms;
  left: -400px;
}

.body,
.header {
  transition: left 400ms;
  left: 0;
}

.overlay {
  transition: opacity 400ms;
  opacity: 0;
}

/* Menu open and animation end positions. */
.is-open .menu {
  left: 0px;
}

.is-open .body,
.is-open .header {
  left: 400px;
}

.is-open .overlay {
  opacity: 0.8;
  bottom: 0;
}