body > header, body > .app.menu, body > main {
  transition: width 0.1s;
}
body > .collapse {
  background: url("action/back.svg") center no-repeat;
  border: none;
  cursor: pointer;
  font-size: 0;
  width: 24px;
}
body.collapse > .collapse {
  background-image: url("action/menu.svg");
}
body.collapse > header, body.collapse > .app.menu {
  width: 0;
}

@media (max-width: 600px) {
  body:not(.collapse) > .app.menu {
    width: calc(100vw - 24px);
  }
  body:not(.collapse) > .collapse {
    min-height: 32px;
  }
  body:not(.collapse) > .breadcrumb, body:not(.collapse) #notifications {
    display: none;
  }
  body:not(.collapse) > main {
    overflow: hidden;
    width: 24px;
  }
  body:not(.collapse) > main > * {
    opacity: 0;
  }
}