.overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  opacity: 0;
  background-color: var(--overlay-default);
}

.menu {
  position: absolute;
  top: 0;
  left: 0;
  height: 100%;
  z-index: 1;
  overflow-y: scroll;
  width: 100%;
  max-width: 20rem;
  background-color: var(--color-white);
}

.closeBtn {
  position: absolute;
  top: 0;
  right: 0;
  padding: var(--size-regular);
  color: var(--color-greyDarker);
}

.closeIcon {
  line-height: 0;
}

.overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  opacity: 0;
  background-color: var(--overlay-default);
}

.menu {
  position: fixed;
  top: 0;
  left: 0;
  height: 100%;
  z-index: 1;
  overflow-y: scroll;
  width: 100%;
  max-width: 20rem;
  background-color: var(--color-white);
}

.closeBtn {
  position: absolute;
  top: 0;
  right: 0;
  padding: var(--size-regular);
  color: var(--color-greyDarker);
}

.closeIcon {
  line-height: 0;
}

Make sidenav the height of page
Make sidenav the height of page
