/* ============================================================
   layout.css — topbar, sidebar, main, toc, responsive grid
   ============================================================ */

/* ---------- Topbar ---------- */
.topbar {
  position: sticky;
  top: 0;
  z-index: 40;
  height: var(--topbar-h);
  display: flex;
  align-items: center;
  gap: var(--sp-3);
  padding: 0 var(--sp-4);
  background: color-mix(in srgb, var(--bg) 82%, transparent);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
}

.brand { display: flex; align-items: center; gap: var(--sp-2); font-weight: 700; letter-spacing: -.02em; white-space: nowrap; }
.brand-mark { font-size: 20px; filter: saturate(1.2); }
.brand-text {
  font-size: 15px;
  background: linear-gradient(92deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text; background-clip: text;
  -webkit-text-fill-color: transparent; color: transparent;
}
/* frontend deck: a thin gradient hairline under the top bar */
.topbar::after {
  content: ""; position: absolute; left: 0; right: 0; bottom: -1px; height: 2px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2), transparent);
  opacity: .6; pointer-events: none;
}
.topbar { position: sticky; }

.search-wrap { position: relative; margin-left: auto; width: min(420px, 42vw); }
.search-icon { position: absolute; left: 12px; top: 50%; transform: translateY(-50%); color: var(--text-3); pointer-events: none; }
#searchInput {
  width: 100%;
  height: 38px;
  padding: 0 38px 0 36px;
  border-radius: var(--r-md);
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  font-size: 14px;
  font-family: inherit;
  transition: border var(--fast), box-shadow var(--fast), background var(--fast);
}
#searchInput:focus { outline: none; border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.search-kbd {
  position: absolute; right: 10px; top: 50%; transform: translateY(-50%);
  font-family: var(--font-mono); font-size: 12px; color: var(--text-3);
  background: var(--bg-3); border: 1px solid var(--border); border-radius: 5px;
  padding: 1px 6px; pointer-events: none;
}

.search-results {
  position: absolute; top: calc(100% + 8px); left: 0; right: 0;
  max-height: 60vh; overflow-y: auto;
  background: var(--elevated); border: 1px solid var(--border);
  border-radius: var(--r-md); box-shadow: var(--shadow);
  padding: var(--sp-2); z-index: 60;
}

/* ---------- App grid ---------- */
.app {
  display: grid;
  grid-template-columns: var(--sidebar-w) minmax(0, 1fr) var(--toc-w);
  align-items: start;
}

/* ---------- Sidebar ---------- */
.sidebar {
  position: sticky;
  top: var(--topbar-h);
  height: calc(100vh - var(--topbar-h));
  overflow-y: auto;
  border-right: 1px solid var(--border);
  padding: var(--sp-4) var(--sp-3) var(--sp-5);
  background: var(--bg);
  display: flex;
  flex-direction: column;
  gap: var(--sp-3);
}

.nav { display: flex; flex-direction: column; gap: 2px; }
.nav-item {
  display: flex; align-items: center; gap: var(--sp-3);
  padding: 9px 11px; border-radius: var(--r-md);
  cursor: pointer; color: var(--text-2); font-size: 14px; font-weight: 500;
  border: 1px solid transparent;
  transition: background var(--fast), color var(--fast), border-color var(--fast), transform var(--fast);
  user-select: none;
}
.nav-item:hover { background: var(--surface); color: var(--text); }
.nav-item.is-active { background: var(--accent-soft); color: var(--text); border-color: color-mix(in srgb, var(--accent) 30%, transparent); }
.nav-item .dot { width: 9px; height: 9px; border-radius: 50%; flex: none; box-shadow: 0 0 0 3px color-mix(in srgb, currentColor 18%, transparent); }
.nav-item .nav-name { flex: 1; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.nav-item .nav-lang { font-size: 10px; color: var(--text-3); text-transform: uppercase; letter-spacing: .04em; }
.nav-group-label { font-size: 10px; text-transform: uppercase; letter-spacing: .1em; color: var(--text-3); padding: var(--sp-3) 11px var(--sp-1); }

/* ---------- Collapsible nav groups (Go / Rust / C++) ---------- */
.nav-group { display: flex; flex-direction: column; }
.nav-group-head {
  display: flex; align-items: center; gap: var(--sp-3);
  padding: 9px 11px; border-radius: var(--r-md);
  cursor: pointer; color: var(--text-2); font-size: 14px; font-weight: 600;
  border: 1px solid transparent; user-select: none;
  transition: background var(--fast), color var(--fast);
}
.nav-group-head:hover { background: var(--surface); color: var(--text); }
.nav-group-head .dot { width: 9px; height: 9px; border-radius: 50%; flex: none; box-shadow: 0 0 0 3px color-mix(in srgb, currentColor 18%, transparent); }
.nav-group-head .nav-name { flex: 1; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.nav-group-count {
  font-size: 10px; color: var(--text-3); background: var(--bg-3);
  border: 1px solid var(--border); border-radius: 999px;
  padding: 0 6px; min-width: 18px; text-align: center; line-height: 16px;
}
.nav-group-head .chev { color: var(--text-3); flex: none; transition: transform var(--fast); }
.nav-group.is-open .nav-group-head .chev { transform: rotate(90deg); }
.nav-group-body {
  display: grid; grid-template-rows: 0fr;
  transition: grid-template-rows var(--med) var(--ease-out);
}
.nav-group.is-open .nav-group-body { grid-template-rows: 1fr; }
.nav-group-inner {
  overflow: hidden; min-height: 0;
  display: flex; flex-direction: column; gap: 2px;
  margin: 2px 0 2px 15px; padding-left: 6px;
  border-left: 1px solid var(--border);
}
.nav-item.is-sub { padding: 7px 10px; font-size: 13px; font-weight: 500; }
.nav-item.is-sub .dot { width: 7px; height: 7px; }

.sidebar-foot { margin-top: auto; padding-top: var(--sp-3); border-top: 1px solid var(--border); }
.deck-stats { font-size: 11px; line-height: 1.5; color: var(--muted); margin-bottom: var(--sp-2); letter-spacing: .01em; }
.deck-stats b { color: var(--text); font-weight: 600; }
.deck-crosslink { display: flex; align-items: center; gap: 7px; padding: 8px 10px; border: 1px solid var(--border); border-radius: 8px; color: var(--muted); font-size: 11.5px; font-weight: 600; text-decoration: none; transition: color .15s ease, border-color .15s ease, background .15s ease; }
.deck-crosslink:hover { color: var(--accent); border-color: var(--accent); background: color-mix(in srgb, var(--accent) 10%, transparent); }
.deck-crosslink-ico { font-size: 13px; line-height: 1; }
.deck-crosslink-text { flex: 1; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.deck-crosslink-arrow { flex-shrink: 0; opacity: .55; transition: opacity .15s ease; }
.deck-crosslink:hover .deck-crosslink-arrow { opacity: 1; }

/* ---------- Main ---------- */
.main { min-width: 0; padding: var(--sp-6) var(--sp-6) var(--sp-7); }
.content { max-width: var(--content-max); margin: 0 auto; }

/* ---------- TOC ---------- */
.toc {
  position: sticky; top: var(--topbar-h);
  height: calc(100vh - var(--topbar-h)); overflow-y: auto;
  padding: var(--sp-6) var(--sp-4);
  font-size: 13px;
}
.toc-title { font-size: 10px; text-transform: uppercase; letter-spacing: .1em; color: var(--text-3); margin-bottom: var(--sp-3); }
.toc a {
  display: block; padding: 5px 10px; color: var(--text-3);
  text-decoration: none; border-left: 2px solid var(--border);
  transition: color var(--fast), border-color var(--fast);
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}
.toc a:hover { color: var(--text-2); }
.toc a.is-active { color: var(--accent); border-left-color: var(--accent); font-weight: 600; }
.toc a.deep-toc { padding-left: 20px; font-size: 12px; opacity: .8; }

.scrim {
  position: fixed; inset: 0; background: var(--scrim); z-index: 35;
  opacity: 0; pointer-events: none; transition: opacity var(--med);
}
body.nav-open .scrim { opacity: 1; pointer-events: auto; }

/* ---------- Responsive ---------- */
@media (max-width: 1100px) {
  .app { grid-template-columns: var(--sidebar-w) minmax(0, 1fr); }
  .toc { display: none; }
}
@media (max-width: 820px) {
  :root { --sidebar-w: 280px; }
  .app { grid-template-columns: minmax(0, 1fr); }
  #menuToggle { display: inline-flex; }
  .sidebar {
    position: fixed; top: var(--topbar-h); left: 0; z-index: 38;
    width: var(--sidebar-w); transform: translateX(-102%);
    transition: transform var(--med) var(--ease-out);
    box-shadow: var(--shadow);
  }
  body.nav-open .sidebar { transform: translateX(0); }
  .brand-text { display: none; }
  .search-wrap { width: auto; flex: 1; }
  .main { padding: var(--sp-4) var(--sp-4) var(--sp-7); }
}
@media (min-width: 821px) { #menuToggle { display: none; } }