/* 平板 */
@media (max-width:1024px){
  .shell{flex-direction:column}
  .shell .side-left,.shell .side-right{width:100%}
}

/* 手机 */
@media (max-width:600px){
  :root{--nav-h:52px}
  .topbar{padding:0 12px;gap:10px}
  .topbar .brand{font-size:.95rem}
  .topbar nav{gap:2px}
  .topbar nav a{padding:5px 8px;font-size:.82rem}
  .shell{padding:12px}
  .concept-grid{grid-template-columns:1fr}
  .anim-controls input[type=range]{width:100%}
  .anim-controls label{width:100%}
  .katex{font-size:.95em}
}

/* 触摸区域 ≥44px */
@media (hover:none){
  .btn,.tree-leaf,.q-opt{min-height:44px}
}