@media (max-width: 640px) {
  /* Nav sidebar - wider overlay with shadow */
  .js-navExpanded .t-Body-nav {
    width: 280px !important;
    box-shadow: 4px 0 20px rgba(0,0,0,0.3);
    z-index: 1000;
  }
  /* Nav items - larger touch targets */
  .t-TreeNav .a-TreeView-content {
    font-size: 15px !important;
    line-height: 48px !important;
    padding: 0 16px !important;
  }
  .t-TreeNav .a-TreeView-node--topLevel {
    min-height: 48px !important;
  }
  /* Fix mobile touch - remove 300ms tap delay */
  .t-TreeNav .a-TreeView-content,
  .t-TreeNav .a-TreeView-toggle,
  .t-TreeNav .a-TreeView li,
  .t-Body-nav {
    touch-action: manipulation;
    -webkit-tap-highlight-color: rgba(255,255,255,0.1);
  }
  /* Nav icons - larger */
  .t-TreeNav .a-TreeView-node--topLevel .fa,
  .t-TreeNav .a-TreeView-node--topLevel .a-Icon {
    font-size: 18px !important;
    width: 24px !important;
    margin-right: 12px !important;
  }
  /* Selected item highlight */
  .t-TreeNav .a-TreeView-node.is-current > .a-TreeView-content {
    background: rgba(255,255,255,0.15) !important;
    border-left: 3px solid #fff !important;
  }
  /* Sub-items */
  .t-TreeNav .a-TreeView-content.a-TreeView-content--level2 {
    font-size: 14px !important;
    line-height: 44px !important;
    padding-left: 48px !important;
  }
  /* Header - touch-friendly */
  .t-Header .t-Button--navBar {
    min-width: 48px !important;
    min-height: 48px !important;
  }
  .t-Header-nav-list a {
    min-height: 44px !important;
    padding: 0 12px !important;
    font-size: 14px !important;
  }
  /* Dark overlay when nav open */
  .js-navExpanded .t-Body-content {
    position: relative;
  }
  .js-navExpanded .t-Body-content::before {
    content: "";
    position: fixed;
    top: 48px;
    left: 280px;
    right: 0;
    bottom: 0;
    background: rgba(0,0,0,0.4);
    z-index: 999;
  }
}