hyper/app/css/tabs.css

nav {
  font-size: 12px;
  font-family: -apple-system, BlinkMacSystemFont,
  "Segoe UI", "Roboto", "Oxygen",
  "Ubuntu", "Cantarell", "Fira Sans",
  "Droid Sans", "Helvetica Neue", sans-serif;
  height: 28px;
  line-height: 28px;
  vertical-align: middle;
  color: #9B9B9B;
  cursor: default;
  user-select: none;
}

.single {
  text-align: center;
  color: #fff;
}

.tabs {
  border-bottom: 1px solid #333;
  max-height: 28px;
  display: flex;
  flex-flow: row;
}

.tabs li:first-child {
  margin-left: 70px;
}

.tabs li {
  list-style-type: none;
  flex-grow: 1;
  text-align: center;
}

.tabs li.is_active {
  color: #fff;
  position: relative;
}

.tabs li span {
  display: block;
    border-left: 1px solid transparent;
    border-right: 1px solid transparent;
}

.tabs li.is_active span {
  border-left-color: #333;
  border-right-color: #333;
}

.tabs li.is_active:last-child span {
  border-right-color: transparent;
}

.tabs li.is_active::before {
  position: absolute;
  content: ' ';
  border-bottom: 1px solid #000;
  display: block;
  left: 1px;
  right: 1px;
  bottom: -1px;
}

.tabs li:not(.is_active):hover {
  color: #ccc;
}

.tabs li.has_activity, .tabs li.has_activity:hover {
  color: #50E3C2;
}