/* ============================================================
     CẤU HÌNH MÀU — đổi accent ở đây để rebrand
     ============================================================ */
  :root {
    --ink:        #15181f;
    --ink-soft:   #4a505c;
    --ink-faint:  #8a91a0;
    --line:       #e6e8ec;
    --line-soft:  #f0f2f5;
    --paper:      #ffffff;
    --side:       #f7f8fa;
    --accent:     #005F07;
    --accent-bg:  #eaf1ff;
    --radius:     10px;
    --side-w:     320px;
  }

  * { box-sizing: border-box; margin: 0; padding: 0; }

  html, body { height: 100%; }

  body {
    font-family: Roboto, sans-serif;
    color: var(--ink);
    background: var(--paper);
    display: flex;
    height: 100vh;
    overflow: hidden;
    -webkit-font-smoothing: antialiased;
  }

  /* ===================== SIDEBAR ===================== */
  .sidebar {
    width: var(--side-w);
    flex-shrink: 0;
    background: var(--side);
    border-right: 1px solid var(--line);
    display: flex;
    flex-direction: column;
    height: 100%;
  }

  .brand {
    padding: 20px 22px 16px;
    border-bottom: 1px solid var(--line);
  }
  .brand h1 {
    font-size: 16px;
    font-weight: 700;
    letter-spacing: -0.01em;
  }
  .brand p {
    font-size: 12.5px;
    color: var(--ink-faint);
    margin-top: 3px;
  }

  .search {
    padding: 14px 18px 8px;
  }
  .search input {
    width: 100%;
    padding: 9px 12px;
    font-size: 13.5px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: var(--paper);
    color: var(--ink);
    outline: none;
    transition: border-color .15s, box-shadow .15s;
  }
  .search input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-bg);
  }
  .search input::placeholder { color: var(--ink-faint); }

  .nav {
    flex: 1;
    overflow-y: auto;
    padding: 6px 12px 18px;
  }

  .group-label {
    font-size: 11px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--ink-faint);
    padding: 14px 10px 6px;
  }

  .nav-item {
    display: flex;
    align-items: center;
    gap: 10px;
    width: 100%;
    text-align: left;
    padding: 9px 10px;
    border: none;
    background: none;
    border-radius: 8px;
    font-size: 13.5px;
    color: var(--ink-soft);
    cursor: pointer;
    transition: background .12s, color .12s;
    line-height: 1.35;
  }
  .nav-item:hover { background: var(--line-soft); color: var(--ink); }
  .nav-item:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 1px;
  }
  .nav-item.active {
    background: var(--accent-bg);
    color: var(--accent);
    font-weight: 600;
  }
  .nav-item .ico {
    flex-shrink: 0;
    width: 18px; height: 18px;
    opacity: .65;
  }
  .nav-item.active .ico { opacity: 1; }

  .nav-empty {
    padding: 18px 12px;
    font-size: 13px;
    color: var(--ink-faint);
  }

  .side-foot {
    border-top: 1px solid var(--line);
    padding: 12px 18px;
  }
  .upload-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 7px;
    width: 100%;
    padding: 9px;
    font-size: 13px;
    font-weight: 500;
    color: var(--ink-soft);
    background: var(--paper);
    border: 1px dashed var(--line);
    border-radius: 8px;
    cursor: pointer;
    transition: border-color .15s, color .15s;
  }
  .upload-btn:hover { border-color: var(--accent); color: var(--accent); }

  /* ===================== VIEWER ===================== */
  .viewer {
    flex: 1;
    display: flex;
    flex-direction: column;
    height: 100%;
    min-width: 0;
  }

  .topbar {
    height: 56px;
    flex-shrink: 0;
    border-bottom: 1px solid var(--line);
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 0 18px;
    background: var(--paper);
  }
  .menu-toggle {
    display: none;
    border: none; background: none; cursor: pointer;
    padding: 6px; border-radius: 6px; color: var(--ink-soft);
  }
  .menu-toggle:hover { background: var(--line-soft); }

  .doc-title {
    font-size: 14.5px;
    font-weight: 600;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    flex: 1;
  }
  .doc-title .muted { color: var(--ink-faint); font-weight: 400; }

  .actions { display: flex; gap: 8px; }
  .act {
    display: flex; align-items: center; gap: 6px;
    padding: 7px 12px;
    font-size: 13px;
    font-weight: 500;
    color: var(--ink-soft);
    background: var(--paper);
    border: 1px solid var(--line);
    border-radius: 8px;
    cursor: pointer;
    text-decoration: none;
    transition: border-color .15s, color .15s, background .15s;
  }
  .act:hover { border-color: var(--accent); color: var(--accent); }
  .act[hidden] { display: none; }

  .stage {
    flex: 1;
    position: relative;
    background: #525659;
    min-height: 0;
  }
  .stage iframe {
    width: 100%;
    height: 100%;
    border: none;
    display: block;
  }

  .empty {
    position: absolute;
    inset: 0;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 14px;
    background: var(--paper);
    color: var(--ink-faint);
    text-align: center;
    padding: 24px;
  }
  .empty svg { opacity: .35; }
  .empty h2 { font-size: 16px; font-weight: 600; color: var(--ink-soft); }
  .empty p { font-size: 13.5px; max-width: 340px; line-height: 1.5; }

  /* ===================== MOBILE ===================== */
  .scrim {
    display: none;
    position: fixed; inset: 0;
    background: rgba(0,0,0,.35);
    z-index: 18;
  }

  @media (max-width: 820px) {
    .sidebar {
      position: fixed;
      left: 0; top: 0; bottom: 0;
      z-index: 20;
      transform: translateX(-100%);
      transition: transform .22s ease;
      box-shadow: 0 0 30px rgba(0,0,0,.15);
    }
    body.nav-open .sidebar { transform: translateX(0); }
    body.nav-open .scrim { display: block; }
    .menu-toggle { display: inline-flex; }
  }

  @media (prefers-reduced-motion: reduce) {
    * { transition: none !important; }
  }