* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Arial, sans-serif;
  line-height: 1.6;
}

#navbar {
  position: fixed;
  top: 0;
  left: 0;
  width: 250px;
  height: 100%;
  background-color: #f4f4f4;
  border-right: 1px solid #ccc;
  padding: 1rem;
  overflow-y: auto;
}

#navbar header {
  font-size: 1.5rem;
  margin-bottom: 1rem;
}

.nav-link {
  display: block;
  margin: 0.5rem 0;
  color: #333;
  text-decoration: none;
}

.nav-link:hover {
  text-decoration: underline;
}

#main-doc {
  margin-left: 270px;
  padding: 2rem;
}

.main-section {
  margin-bottom: 3rem;
}

code {
  display: block;
  background: #eee;
  padding: 0.5rem;
  margin: 0.5rem 0;
  border-left: 3px solid #ccc;
}

ul {
  padding-left: 1.5rem;
}

/* media query */
@media (max-width: 768px) {
  #navbar {
    position: static;
    width: 100%;
    height: auto;
    border-right: none;
    border-bottom: 1px solid #ccc;
  }

  #main-doc {
    margin: 0;
    padding: 1rem;
  }
}