.back-top{
    position:fixed;
    right:30px;
    bottom:30px;

    width:60px;
    height:60px;

    border-radius:50%;

    display:flex;
    align-items:center;
    justify-content:center;

    background:rgba(255,255,255,.15);
    backdrop-filter:blur(10px);

    color:#fff;
    text-decoration:none;

    font-size:12px;
    letter-spacing:.15em;

    border:1px solid rgba(255,255,255,.3);

    z-index:1000;

    transition:.3s;
}

.back-top:hover{
    background:rgba(255,255,255,.35);
    transform:translateY(-5px);
}

@media(max-width:767px){

    .back-top{
        right:20px;
        bottom:20px;

        width:50px;
        height:50px;
    }

}

html,
body {
  position: relative;
  height: 100%;
}

body {
  display: flex;
  flex-direction: column;
  margin: 0;
  padding: 0;
  line-height: 1.5;
  font-family: -apple-system, system-ui, "Helvetica Neue", Helvetica, Arial, "Segoe UI", Roboto, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.demo-nav {
  height: 56px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: #212121;
  box-sizing: border-box;
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

button {
  appearance: none;
  cursor: pointer;
  background: transparent;
  border: 1px solid #aaa;
  color: #aaa;
  height: 32px;
  font-weight: bold;
  border-radius: 8px;
  padding: 0 16px;
}
button + button {
  margin-left: 16px;
}
button:hover {
  background: rgba(255, 255, 255, 0.1);
}
button.active {
  background: #114df1;
  border-color: #114df1;
  color: #fff;
}

iframe {
  height: 100%;
  flex-shrink: 10;
  min-height: 0;
}