style.css

p.caption {
  color: #777;
  margin-top: 10px;
}
p code {
  white-space: inherit;
}
pre {
  word-break: normal;
  word-wrap: normal;
}
pre code {
  white-space: inherit;
}
.practice {
    padding: 1em;
    margin: 1em 0;
    padding-left: 100px;
    background-size: 50px;
    background-repeat: no-repeat;
    background-position: 15px center;
    min-height: 100px;
    color: #1f5386;
    background-color: #f5f5f5;
    background-image: url("fig/book-open.png");
}
.practice > :first-child:before {
  font-weight: bold;
  content: "Practice: ";
}
.example {
    background-size: 30px;
    background-repeat: no-repeat;
    background-position: 15px center;
    background-color: #fff5ee;
}
.define {
    padding: 1em;
    margin: 1em 0;
    padding-left: 100px;
    background-size: 50px;
    background-repeat: no-repeat;
    background-position: 15px center;
    min-height: 100px;
    color: #1f5386;
    background-color: #f5f5f5;
    background-image: url("fig/bookmark.png");
}
.define > :first-child:before {
  font-weight: bold;
  content: "Definition: ";
}
.caution {
    padding: 1em;
    margin: 1em 0;
    padding-left: 100px;
    background-size: 50px;
    background-repeat: no-repeat;
    background-position: 15px center;
    min-height: 100px;
    color: #1f5386;
    background-color: #f5f5f5;
    background-image: url("fig/caution.png");
}
.objective {
    padding: 1em;
    margin: 1em 0;
    padding-left: 100px;
    background-size: 50px;
    background-repeat: no-repeat;
    background-position: 15px center;
    min-height: 100px;
    color: #1f5386;
    background-color: #f5f5f5;
    background-image: url("fig/target.png");
}
.objective > :first-child:before {
   font-weight: bold;
   content: "Learning objective: ";
}
.center {
  text-align: center;
}