:root{
  /* Flat system. Cards have NO shadow — they are grey fills.
     Only floating layers (modals, dropdowns) lift, and only slightly. */
  --shadow-none:none;
  --shadow-overlay:0 1px 4px rgba(0,0,0,.16);
  --shadow-dropdown:0 1px 6px rgba(0,0,0,.20);
  --shadow-bar:0 -1px 0 var(--grey-200);
}