@media (max-width:900px){
  .topbar{position:relative;z-index:25}
  .menu-button{position:relative;z-index:31;width:42px;height:42px;border-radius:8px;background:var(--surface,#fff);box-shadow:0 2px 8px rgba(0,0,0,.08)}
  .sidebar.open{box-shadow:12px 0 32px rgba(0,0,0,.24)}
}