body {
  font-family: 'Segoe UI', sans-serif;
  background: #f4f6f9;
}

.sidebar {
  min-height: 100vh;
  background: #212529;
  color: white;
  padding: 20px;
}

.sidebar a {
  color: #fff;
  text-decoration: none;
  display: block;
  padding: 8px 0;
}

.sidebar a:hover {
  text-decoration: underline;
}

.content {
  padding: 40px;
}

.materi-box {
  background: white;
  padding: 25px;
  border-radius: 10px;
  box-shadow: 0 5px 15px rgba(0,0,0,.1);
  margin-bottom: 30px;
}