menu.css

/* Menu
-------------------------------------------------- */

.menu-container {
  padding: 0;
  background: none;
}

.menu,
.menu li { border: none; }

.menu li:first-child > a {
  border-top: 1px solid #e5e5e5;
  border-radius: 3px 3px 0 0;
}

.menu li:last-child > a {
  border-bottom: 1px solid #e5e5e5;
  border-radius: 0 0 3px 3px;
}

.menu a {
  border: solid #e5e5e5;
  border-width: 1px 1px 0;
}

.menu a.selected {
  position: relative;
  box-shadow: none;
  border-left: 1px solid #e5e5e5;
  border-top-left-radius: 0 !important;
  border-bottom-left-radius: 0 !important;
}

.menu a.selected::before {
  content: '';
  display: block;
  position: absolute;
  top: 0;
  bottom: 0;
  left: -1px;
  width: 2px;
  background: #d26911;
  box-shadow: 0 1px 0 #d26911, 0 -1px 0 #d26911;
}

.accordion .section a.section-head,
li.usage-bar { border: 1px solid #e5e5e5; }

.accordion .section a.section-head { box-shadow: none; }

li.usage-bar:last-child { border-bottom: 1px solid #e5e5e5; }

.accordion .section .section-nav li:first-child > a,
.accordion .section:not(:first-child) > a.section-head { border-top: none; }

.accordion .section:last-child .section-nav li:last-child { border-radius: 0 0 3px 3px; }

.section-nav li > a { border-radius: 0 !important; }

.accordion .section .section-nav.expanded { position: relative; }

/* Uber-hardcore hack: DO NOT TRY THIS AT HOME */
.accordion .section .section-nav.expanded::before,
.accordion .section .section-nav.expanded::after {
  content: '';
  display: block;
  position: absolute;
  top: -5px;
  width: 4px;
  height: 4px;
  background: #f5f5f5;
  border: solid #e5e5e5;
  border-width: 0 1px 1px;
}

.accordion .section .section-nav.expanded::before {
  left: 0;
  border-right: none;
}

.accordion .section .section-nav.expanded::after {
  right: 0;
  border-left: none;
}