::selection {
  background: #e74c3c; /* WebKit/Blink Browsers */
}
::-moz-selection {
  background: #e74c3c; /* Gecko Browsers */
}

.exercise code {
  color: #f8f8f8;
}
.exercise code a {
  color: #f8f8f8;
}
.exercise span {
  color: #f8f8f8;
}