body {
  padding-top: 50px;
}
.sidebar {
  display:block;
}
@media (min-width: 768px) {
  .sidebar {
    position: fixed;
    top: 51px;
    bottom: 0;
    left: 0;
    z-index: 1000;
    display: block;
    padding: 20px;
    overflow-x: hidden;
    overflow-y: auto; /* Scrollable contents if viewport is shorter than content. */
    background-color: #f5f5f5;
  }
}
.main {
  padding: 20px;
}
@media (min-width: 768px) {
  .main {
    padding-right: 40px;
    padding-left: 40px;
  }
}