home-assistant.io/sass/homeassistant/base/_navigation.scss

/*
 * Navigataur: A pure CSS responsive navigation menu
 * Author: Mike King (@micjamking)
 */

/*--------------------------------
 Functional Styles (Required)
---------------------------------*/
/* Tim Pietrusky advanced checkbox hack (Android <= 4.1.2) */
body {
  -webkit-animation: bugfix infinite 1s;
}
@-webkit-keyframes bugfix {
  from {
    padding: 0;
  }
  to {
    padding: 0;
  }
}

.header {
  position: relative;
}
#toggle,
.toggle {
  display: none;
}
.menu li {
  list-style: none;
  float: left;
}

$menu-collapse: 1024px;

// @media only screen and (max-width: $lap-end){
@media only screen and (max-width: $menu-collapse) {
  .menu {
    display: none;
    opacity: 0;
    width: 100%;
    position: absolute;
    right: 0;
  }
  .menu li {
    display: block;
    width: 100%;
    margin: 0;
  }
  .menu li a {
    display: block;
    width: 100%;
    text-decoration: none;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
  }
  .menu li a .icon {
    display: none;
  }
  .toggle {
    display: block;
    position: relative;
    cursor: pointer;
    -webkit-touch-callout: none;
    -webkit-user-select: none;
    user-select: none;
  }
  #toggle:checked ~ .menu {
    display: block;
    opacity: 1;
    z-index: 999;
  }
}

/* support for submenus */
ul.menu li {
  position: relative;
  margin: 0;

  &:hover ul {
    display: block;
  }

  ul {
    display: none;

    z-index: 10;
    position: absolute;
    top: 68px;

    margin-left: 0;
    background-color: white;
    border-radius: 16px;
    box-shadow: 0 0 1px rgba(0,0,0,.5), 0 32px 64px rgba(0,0,0,.1);

    li {
      white-space: nowrap;
      float: none;

      a {
        display: block;
        padding: 16px 16px;
        min-width: 150px;
        margin: 8px;
        border-radius: 8px;

        &:hover,
        &:focus {
          background: rgba($primary-color, .1);
        }
      }
    }
  }
}

/*--------------------------------
 Presentation Styles (Editable)
---------------------------------*/
header .grid {
  height: 68px;
}

.menu {
  margin: 0;
  top: 68px;
}

.menu li a {
  @include box-sizing(border-box);
  display: block;
  padding: 27px 12px;
  text-decoration: none;
  font-weight: normal;
  font-size: 14px;
  line-height: 1;
}

.menu > li > a:hover,
.menu > li > a:focus {
  background: $site-background;
  box-shadow: inset 0px 5px $primary-color;
  color: $navigation-color;
  padding-bottom: 32px;
}

.toggle {
  z-index: 20;
}

@media only screen and (max-width: $menu-collapse) {
  .menu {
    background: $white;
    box-shadow: 0px 64px 32px rgba(0,0,0,.1);
    max-height: 100vh;
    overflow-y: auto;
  }

  .menu,
  .menu li,
  .menu li a {
    height: auto;
  }

  .menu li a {
    margin: 0 !important;
    padding: 20px 24px !important;
  }

  .menu li a:hover,
  .menu li a:focus {
    background: rgba($primary-color, .1);
    box-shadow: inset 5px 0px $primary-color;
    padding: 15px 15px 15px 25px;
  }

  .toggle {
    position: absolute;
    top: 17px;
    right: 17px;
  }

  .toggle::after {
    @include box-sizing(border-box);
    @include transition(all 0.5s linear);
    content: "☰";
    display: flex;
    justify-content: center;
    align-items: center;
    width: 32px;
    height: 32px;
    background: $primary-color;
    text-align: center;
    font-family: $sans-serif;
    color: $white;
    white-space: nowrap;
    border-radius: 24px;
  }

  .toggle:hover::after {
    background: darken($primary-color, 25%);
  }

  #toggle:checked + .toggle::after {
    content: attr(data-close);
    padding-bottom: 2px;
  }

  /* submenus */
  ul.menu li ul {
    display: block;
    position: relative;
    top: 0;
    box-shadow: none;
    margin-left: 24px;
  }
}