body {
  margin: 0;
  font-family: Arial, sans-serif;
  background: #111;
  color: #eee;
}

.slide {
  display: none;
  padding: 40px;
  box-sizing: border-box;
  height: 100vh;
}

.slide.active { display: block; }

h1, h2, h3 { margin-top: 0; }

/* Lesson 2 originally specified white headings. */
body.ljt-lesson-2 h1,
body.ljt-lesson-2 h2,
body.ljt-lesson-2 h3 { color: #fff; }

.ref { font-style: italic; color: #ccc; }

ul { margin-top: 10px; }

/* Lesson 2 originally adds this left margin. */
body.ljt-lesson-2 ul { margin-left: 20px; }

.nav {
  position: fixed;
  bottom: 10px;
  left: 0;
  right: 0;
  text-align: center;
  z-index: 10;
}

.nav button {
  margin: 0 10px;
  padding: 8px 16px;
  font-size: 14px;
  cursor: pointer;
}

.footer {
  position: fixed;
  bottom: 10px;
  right: 20px;
  font-size: 12px;
  color: #888;
}