/* ============================================================
   LAYOUT — app shell, topbar, two-column tool layout
   ============================================================ */

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: 14px;
  line-height: 1.6;
  min-height: 100vh;
}
a { color: inherit; text-decoration: none; }
button { font-family: inherit; cursor: pointer; }
img { display: block; max-width: 100%; }

/* ---- Topbar ---- */
.topbar {
  position: sticky;
  top: 0;
  z-index: 50;
  height: var(--topbar-h);
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  box-shadow: var(--shadow-sm);
}
.topbar-inner {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 20px;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}
.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 15px;
  color: var(--text);
  white-space: nowrap;
}
.brand img { height: 32px; width: auto; }
.brand-sep { color: var(--border-dark); font-weight: 300; }
.brand-tool { color: var(--accent-dark); font-size: 13px; }

.nav-links {
  display: flex;
  align-items: center;
  gap: 4px;
}
.nav-link {
  padding: 6px 12px;
  border-radius: var(--radius-sm);
  font-size: 13px;
  font-weight: 500;
  color: var(--text-muted);
  transition: background .15s, color .15s;
}
.nav-link:hover { background: var(--bg); color: var(--text); }
.nav-link.active { background: var(--accent-soft); color: var(--accent-dark); font-weight: 600; }

/* ---- Page wrapper ---- */
.page-wrap {
  max-width: 1400px;
  margin: 0 auto;
  padding: 24px 20px 40px;
}

/* ---- Tool layout: left panel + right preview ---- */
.tool-layout {
  display: grid;
  grid-template-columns: var(--sidebar-w) 1fr;
  gap: 20px;
  align-items: start;
}
.tool-panel {
  position: sticky;
  top: calc(var(--topbar-h) + 16px);
  max-height: calc(100vh - var(--topbar-h) - 32px);
  overflow-y: auto;
  scrollbar-width: thin;
  scrollbar-color: var(--border) transparent;
}
.tool-panel::-webkit-scrollbar { width: 6px; }
.tool-panel::-webkit-scrollbar-thumb { background: var(--border); border-radius: 99px; }
.tool-panel::-webkit-scrollbar-thumb:hover { background: var(--border-dark); }

.tool-preview {
  min-height: calc(100vh - var(--topbar-h) - 80px);
}

/* ---- Page header (breadcrumb + title) ---- */
.page-header { margin-bottom: 20px; }
.breadcrumb {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 12px;
  color: var(--text-muted);
  margin-bottom: 8px;
}
.breadcrumb a { color: var(--text-muted); }
.breadcrumb a:hover { color: var(--accent-dark); }
.breadcrumb-sep { color: var(--border-dark); }
.page-title {
  font-size: 22px;
  font-weight: 700;
  color: var(--text);
  line-height: 1.3;
}
.page-desc {
  margin-top: 4px;
  font-size: 13px;
  color: var(--text-muted);
}

/* ---- Footer ---- */
.site-footer {
  border-top: 1px solid var(--border);
  background: var(--surface);
  padding: 20px;
  text-align: center;
  font-size: 12px;
  color: var(--text-muted);
  font-family: var(--font-mono);
}
.site-footer a { color: var(--text-muted); }
.site-footer a:hover { color: var(--accent-dark); }

/* ---- Responsive ---- */
@media (max-width: 900px) {
  .tool-layout { grid-template-columns: 1fr; }
  .tool-panel { position: static; max-height: none; overflow-y: visible; }
}
@media (max-width: 600px) {
  .page-wrap { padding: 16px 14px 32px; }
  .topbar-inner { padding: 0 14px; }
  .page-title { font-size: 18px; }
  .nav-links { display: none; }
}