html, 
body {
}

.button-panel {
  height: 100%;
  text-align: center;
  vertical-align: middle;
}

.button-panel-wrapper {
  display: inline-block;
  vertical-align: middle;
}

.button-panel a {
  display: inline-block;
  vertical-align: middle;
  color: #000;
}
.button-panel::after {
  content: "";
  display: inline-block;
  height: 100%;
  vertical-align: middle;
}

iframe {
}