del {
  position: relative;
  text-decoration: none;
}

del::after {
  content: "";
  border-bottom: 6px solid red;
  position: absolute;
  left: 0;
  top: 50%;
  width: 100%;
}

.reveal pre,
.reveal code {
  border-radius: 15px;
}
.reveal pre code {
  max-height: 600px;
}