body {
  background: #FFDDDD;
  color: #800000;
}
h1 { color:black; }
h2{
  color: white;
  background: #400000;
  padding: 5px;
}
.formula {
  font-style: italic;
  font-weight: bold;
  text-align: center;
}
.definition {
  border: 1px solid;
  padding: 10px;
}