.sidebar-toggle {
  display: none;
}

.sidebar-backdrop {
  display: none;
}

@media (max-width: 900px) {
  body {
    overflow-x: hidden;
  }

  .layout {
    position: relative;
  }

  .sidebar {
    display: flex;
    position: fixed;
    top: 0;
    left: 0;
    bottom: 0;
    width: 82%;
    max-width: 320px;
    transform: translateX(-100%);
    transition: transform 0.3s ease;
    z-index: 1001;
    box-shadow: 14px 0 36px rgba(15, 23, 42, 0.25);
  }

  body.sidebar-open .sidebar {
    transform: translateX(0);
  }

  .sidebar-backdrop {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.35);
    z-index: 1000;
  }

  body.sidebar-open .sidebar-backdrop {
    display: block;
  }

  body:not(.sidebar-open) .sidebar-backdrop {
    display: none;
  }

  .main {
    flex: 1;
    min-height: 100vh;
  }

  .topbar {
    padding: 0 16px;
    gap: 12px;
  }

  .sidebar-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 44px;
    height: 44px;
    border-radius: 14px;
    border: 1px solid var(--divider);
    background: #ffffff;
    color: #111827;
    font-size: 20px;
    line-height: 1;
    cursor: pointer;
    box-shadow: 0 10px 24px rgba(15, 23, 42, 0.08);
  }

  .topbar-left {
    font-size: 12px;
    letter-spacing: 0.16em;
  }

  .topbar-right {
    margin-left: auto;
    font-size: 10px;
    letter-spacing: 0.12em;
  }

  .canvas {
    padding: 16px;
  }

  .chat-shell {
    align-items: stretch;
  }

  .galen-block {
    margin-top: 32px;
  }
}