@media screen {
  html.focus-fallback:has(.book-reader-nav) { position: static; inset: auto; }
  :is(.cover-page, .toc-page, [id^="lesson-"]) { scroll-margin-top: var(--book-reader-offset, 24px); }
  .book-reader-nav {
    position: fixed;
    right: max(16px, env(safe-area-inset-right));
    bottom: max(16px, env(safe-area-inset-bottom));
    z-index: 100020;
    display: flex;
    gap: 6px;
    padding: 4px;
    border: 1px solid #9eafa6;
    border-radius: 12px;
    background: #fffdf7;
    box-shadow: 0 3px 0 #d7dbc5;
  }
  body:has(.reader-toolbar):not(.lesson-focus) .book-reader-nav { display: none; }
  .book-reader-nav a {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 44px;
    padding: 0 12px;
    border-radius: 8px;
    color: #225777;
    font: 700 15px/1.4 "PingFang TC", system-ui, sans-serif;
    text-decoration: none;
  }
  .book-reader-nav a:hover { background: #e4f2ff; }
  .book-reader-nav a:focus-visible { outline: 3px solid #e69a16; outline-offset: 2px; }
}

@media print {
  .book-reader-nav,.reader-toolbar,.site-language-switch { display:none !important; }
}