.site-wrapper {
  display: grid;
  grid-template-columns: 280px 1fr;
  min-height: 100vh;
  max-width: 1500px;
  margin: 0 auto;
  border-left: 1px solid var(--line);
  border-right: 1px solid var(--line);
  background: var(--bg);
}

main {
  min-width: 0;
  border-left: 1px solid var(--line);
}

.site-header {
  display: none;
}

/* off-canvas overlay: out of grid flow until the mobile menu opens */
.sidebar-overlay {
  display: none;
}

/* ---------- sidebar ---------- */
.sidebar {
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
  background: var(--bg);
}

.sidebar-close {
  display: none;
}

.brand {
  padding: 1.5rem 1.25rem 1.25rem;
  border-bottom: 1px solid var(--line);
}

.brand a {
  font: 700 1.05rem var(--disp);
  letter-spacing: 0.01em;
}

.brand a span {
  color: var(--l1);
}

.brand .tag {
  display: block;
  font: 400 0.68rem var(--mono);
  color: var(--dim);
  margin-top: 0.35rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.lvl-nav {
  padding: 0.75rem 0 1rem;
}

.lvl {
  border-bottom: 1px solid var(--line);
}

.lvl summary {
  list-style: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.8rem 1.25rem;
  font: 500 0.8rem var(--mono);
  letter-spacing: 0.04em;
  color: var(--muted);
}

.lvl summary::-webkit-details-marker { display: none; }

.lvl summary .dotc {
  width: 8px;
  height: 8px;
  flex: none;
  background: var(--lc);
}

.lvl summary b { color: var(--ink); font-weight: 500; }

.lvl summary .n { margin-left: auto; color: var(--dim); font-size: 0.68rem; }

.lvl[open] summary { color: var(--ink); }

.lvl ul { list-style: none; padding: 0 0 0.6rem; }

.lvl li { margin: 0; }

.lvl li a {
  display: flex;
  gap: 0.6rem;
  padding: 0.42rem 1.25rem 0.42rem 2.05rem;
  font-size: 0.82rem;
  color: var(--muted);
  border-left: 2px solid transparent;
}

.lvl li a:hover,
.lvl li a[aria-current="page"] {
  color: var(--ink);
  border-left-color: var(--lc);
  background: var(--panel);
}

.lvl li a .idx {
  font: 500 0.72rem/1.7 var(--mono);
  color: var(--lc);
  opacity: 0.85;
}

.side-foot {
  padding: 1rem 1.25rem;
  font: 400 0.72rem var(--mono);
  color: var(--dim);
  border-top: 1px solid var(--line);
}

.side-foot a { color: var(--muted); }
.side-foot a:hover { color: var(--l1); }

.menu-toggle { display: none; }

@media (max-width: 900px) {
  .site-wrapper {
    grid-template-columns: 1fr;
    border-left: 0;
    border-right: 0;
  }

  main { border-left: 0; }

  .site-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0.75rem 1rem;
    background: var(--panel);
    border-bottom: 1px solid var(--line);
    position: sticky;
    top: 0;
    z-index: 50;
  }

  .site-header a {
    font: 700 1rem var(--disp);
  }

  .site-header a span { color: var(--l1); }

  .menu-toggle {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    background: transparent;
    border: 1px solid var(--line);
    color: var(--ink);
    padding: 0.5rem 0.8rem;
    font: 500 0.75rem var(--mono);
    cursor: pointer;
  }

  .sidebar {
    position: fixed;
    left: 0;
    top: 0;
    width: 280px;
    transform: translateX(-100%);
    transition: transform 0.2s ease;
    z-index: 60;
    border-right: 1px solid var(--line);
  }

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

  .sidebar-close {
    display: block;
    position: absolute;
    top: 0.6rem;
    right: 0.6rem;
    background: transparent;
    border: 1px solid var(--line);
    color: var(--ink);
    width: 32px;
    height: 32px;
    font: 400 1.1rem var(--mono);
    line-height: 1;
    cursor: pointer;
  }

  .sidebar-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.6);
    z-index: 55;
  }

  .sidebar-overlay.open { display: block; }
}