.opg {
    margin: auto;
    margin-bottom: 2em;
    margin-top: 2em;
    border: 1px solid #d8dae1;
    padding: 1rem;
    border-radius: 5px;
}

.video {
    margin: auto;
    margin-bottom: 2em;
    width: 650px;
    border: 1px solid #d8dae1;
    padding: 1rem;
    border-radius: 5px;
}

li { margin: 0.5em }

.preview-btn { float: right; }

.indexnumber {
    text-align: center;
    width:  50px;
}

nav a.current {
  color: #0d47a1 !important;
  border-color: #0d47a1 !important;
}