p.caption {
  color: #777;
  margin-top: 10px;
}
p code {
  white-space: inherit;
}
pre {
  word-break: normal;
  word-wrap: normal;
}
pre code {
  white-space: inherit;
}

.container {
    position: relative;
    width: 100%;
    height: 0;
    padding-bottom: 56.25%;
}
.video {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

.blackbox {
  padding: 1em;
  background: black;
  color: white;
  border: 2px solid orange;
  border-radius: 10px;
}
.center {
  text-align: center;
}

.infobox {
  padding: 1em 1em 1em 4em;
  margin-bottom: 10px;
  border: 2px solid orange;
  border-radius: 10px;
  background: white 10px top/3em no-repeat;
  background-position: 10px 25px;
}

.caution {
  background-image: url("pics/sheep.jpg");
}

.objectives {
  padding: 1em 1em 1em 1em;
  margin-bottom: 15px;
  border: 2px solid #2196F3;
  border-radius: 10px;
  background-color: #E3F2FD;
}

.objectives strong {
  color: #1565C0;
}

<style type="text/css">
    ol { list-style-type: lower-alpha; }
</style>