@media (max-width: 768px) {
  .navbar-collapse {
    position: absolute;
    top: 54px;
    left: 0;
    padding-left: 15px;
    padding-right: 15px;
    padding-bottom: 15px;
    width: 100%;
  }
  .navbar-collapse.collapsing {
    height: auto;
    -webkit-transition: left 0.3s ease;
    -o-transition: left 0.3s ease;
    -moz-transition: left 0.3s ease;
    transition: left 0.3s ease;
    left: -100%;
  }
  .navbar-collapse.show {
    left: 0;
    -webkit-transition: left 0.3s ease-in;
    -o-transition: left 0.3s ease-in;
    -moz-transition: left 0.3s ease-in;
    transition: left 0.3s ease-in;
  }
}