.tab-group {
  margin: 0 13px;
  padding: 0;
}

.tab-group-openers {
  display: block;
  background: #777;
  color: white;
  line-height: 40px;
  font-size: 16px;
  margin: 0;
}

.tab-opener {
  display: inline-block;
  padding: 0 13px;
  cursor: pointer;
  transition: color .3s ease, background .3s ease;
}

.tab-opener.tab-visible {
  color: black;
  background: white;
}

.tab {
  padding: 13px 31px;
  background: white;
  color: black;
}