nav-panel/css/nav-panel.css

A collapsible navigation panel for web pages

.np-collapsible:not(.np-expanded) {
  display: none;
}

.np-transitioning-width {
  width: 0;
  overflow: hidden;
  transition: width 0.25s ease;
}

.np-transitioning-height {
  height: 0;
  overflow: hidden;
  transition: height 0.25s ease;
}