/* ================================================================
   math.css — Modern Math Foundations page styles.
   Designed for chapterN-math.html pages across all hubs.
   Relies on study-base.css / study.css design tokens.
   ================================================================ */

/* ── Back Bar (sticky top nav) ── */
.back-bar {
  position: sticky;
  top: 0;
  z-index: 50;
  background: var(--dark-bg);
  border-bottom: 1px solid rgba(var(--hero-border-rgb), 0.18);
  padding: 0.65rem 2rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
}
.back-bar a {
  color: rgba(var(--hero-highlight-rgb), 0.9);
  text-decoration: none;
  font-size: 0.82rem;
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.3rem 0.65rem;
  border-radius: 8px;
  transition: all 0.2s ease;
  background: transparent;
}
.back-bar a:hover {
  background: rgba(var(--accent-rgb), 0.15);
  color: #fff;
}
.back-bar .page-title-bar {
  font-size: 0.72rem;
  color: rgba(var(--sidebar-text-rgb), 0.5);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  font-weight: 600;
}

#mainContent { margin-left: 0; }

/* ── TOC Sidebar ── */
.toc-sidebar {
  position: fixed;
  top: 46px;
  left: 0;
  width: var(--sidebar-w);
  height: calc(100vh - 46px);
  background: var(--dark-bg);
  border-right: 1px solid rgba(var(--hero-border-rgb), 0.12);
  overflow-y: auto;
  padding: 1.5rem 0 2rem;
  z-index: 40;
  scrollbar-width: thin;
  scrollbar-color: rgba(var(--accent-rgb), 0.2) transparent;
}
.toc-sidebar::-webkit-scrollbar { width: 4px; }
.toc-sidebar::-webkit-scrollbar-track { background: transparent; }
.toc-sidebar::-webkit-scrollbar-thumb { background: rgba(var(--accent-rgb), 0.25); border-radius: 2px; }

.toc-sidebar .home-link {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  color: rgba(var(--sidebar-text-rgb), 0.5);
  text-decoration: none;
  font-size: 0.78rem;
  font-weight: 500;
  padding: 0.4rem 1.5rem 0.6rem;
  transition: color 0.2s;
}
.toc-sidebar .home-link:hover { color: rgba(var(--sidebar-text-rgb), 0.85); }

.toc-sidebar .sidebar-brand {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.25rem 1.5rem 1.25rem;
  border-bottom: 1px solid rgba(var(--hero-border-rgb), 0.12);
  margin-bottom: 0.75rem;
}
.toc-sidebar .sidebar-brand .brand-icon { font-size: 1.3rem; }
.toc-sidebar .sidebar-brand h2 {
  font-size: 1rem;
  font-weight: 700;
  color: rgba(var(--sidebar-text-rgb), 0.92);
  letter-spacing: -0.01em;
}

.toc-sidebar ul { list-style: none; padding: 0; }

.toc-sidebar li a,
.toc-sidebar a.toc-link {
  display: block;
  padding: 0.5rem 1.5rem 0.5rem 1.75rem;
  color: rgba(var(--sidebar-text-rgb), 0.55);
  text-decoration: none;
  font-size: 0.8rem;
  font-weight: 500;
  border-left: 2px solid transparent;
  transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
  position: relative;
}
.toc-sidebar li a:hover,
.toc-sidebar a.toc-link:hover {
  color: rgba(var(--sidebar-text-rgb), 0.9);
  background: rgba(var(--accent-rgb), 0.06);
  padding-left: 2rem;
}
.toc-sidebar li a.active,
.toc-sidebar a.toc-link.active {
  color: #fff;
  border-left-color: rgba(var(--accent-rgb), 1);
  background: linear-gradient(90deg, rgba(var(--accent-rgb), 0.14), transparent 80%);
  font-weight: 600;
}

.toc-group {
  font-size: 0.65rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: rgba(var(--sidebar-text-rgb), 0.3);
  padding: 1rem 1.5rem 0.35rem;
  margin-top: 0.4rem;
  font-weight: 700;
}

.toc-sidebar .back-to-study {
  display: block;
  margin: 1.5rem 1.25rem 0;
  padding: 0.55rem 1rem;
  font-size: 0.78rem;
  font-weight: 600;
  color: rgba(var(--accent-rgb), 0.85);
  text-decoration: none;
  border: 1px solid rgba(var(--accent-rgb), 0.2);
  border-radius: 10px;
  text-align: center;
  transition: all 0.25s ease;
}
.toc-sidebar .back-to-study:hover {
  background: rgba(var(--accent-rgb), 0.12);
  border-color: rgba(var(--accent-rgb), 0.4);
  color: #fff;
}

/* ── Main Content Area ── */
.math-content {
  margin-left: var(--sidebar-w);
  padding-bottom: 4rem;
}
.math-content .section {
  max-width: 880px;
  padding: 2rem 2.5rem;
}

/* ── Hero Header (first section) ── */
.math-hero {
  background: linear-gradient(135deg, rgba(var(--dark-rgb), 0.95), rgba(var(--dark-2-rgb), 0.9));
  border-bottom: 1px solid rgba(var(--hero-border-rgb), 0.18);
  padding: 3rem 2.5rem 2.5rem;
  position: relative;
  overflow: hidden;
}
.math-hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 600px 400px at 20% 50%, rgba(var(--accent-rgb), 0.08), transparent),
    radial-gradient(ellipse 500px 300px at 80% 30%, rgba(var(--secondary-rgb), 0.06), transparent);
  pointer-events: none;
}
.math-hero .hero-tag {
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: rgba(var(--accent-rgb), 0.8);
  font-weight: 700;
  margin-bottom: 0.75rem;
}
.math-hero h1 {
  font-size: clamp(1.6rem, 3vw, 2.2rem);
  font-weight: 800;
  color: var(--hero-text);
  line-height: 1.2;
  letter-spacing: -0.02em;
  margin-bottom: 0.75rem;
}
.math-hero .hero-desc {
  font-size: 0.92rem;
  color: rgba(var(--sidebar-text-rgb), 0.65);
  line-height: 1.6;
  max-width: 600px;
}

/* ── Symbol Table ── */
.symbol-grid {
  display: grid;
  grid-template-columns: auto 1fr 1fr;
  gap: 0;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  margin: 1.75rem 0;
  font-size: 0.88rem;
  box-shadow: 0 4px 24px rgba(var(--shadow-card-rgb), 0.06);
}
.sym-header {
  background: rgba(var(--section-bg-2-rgb), 0.7);
  padding: 0.7rem 1.1rem;
  font-weight: 700;
  color: var(--text-dim);
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  border-bottom: 1px solid var(--border);
}
.sym-cell {
  padding: 0.75rem 1.1rem;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  transition: background 0.15s;
}
.sym-cell:nth-child(3n+1) {
  background: rgba(var(--section-bg-2-rgb), 0.4);
  justify-content: center;
  font-size: 1.15rem;
}
.sym-cell:nth-child(3n+2) {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: var(--accent);
  font-weight: 500;
}

/* ── Definition / Theorem / Example Boxes ── */
.def-box {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-left: 4px solid var(--accent);
  border-radius: 4px var(--radius) var(--radius) 4px;
  padding: 1.4rem 1.75rem;
  margin: 1.5rem 0;
  box-shadow: 0 2px 16px rgba(var(--shadow-card-rgb), 0.05);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
  position: relative;
  overflow: hidden;
}
.def-box::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 4px;
  height: 100%;
  background: linear-gradient(180deg, var(--accent), rgba(var(--accent-rgb), 0.3));
  border-radius: 2px 0 0 2px;
}
.def-box:hover {
  transform: translateY(-1px);
  box-shadow: 0 6px 28px rgba(var(--shadow-card-rgb), 0.1);
}
.def-box .def-label {
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--accent);
  margin-bottom: 0.6rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

.def-box.theorem-box { border-left-color: var(--purple); }
.def-box.theorem-box::before { background: linear-gradient(180deg, var(--purple), rgba(var(--secondary-rgb), 0.3)); }
.def-box.theorem-box .def-label { color: var(--purple); }

.def-box.example-box { border-left-color: var(--green); }
.def-box.example-box::before { background: linear-gradient(180deg, var(--green), rgba(22, 128, 91, 0.3)); }
.def-box.example-box .def-label { color: var(--green); }

.def-box.warning-box { border-left-color: var(--yellow); }
.def-box.warning-box::before { background: linear-gradient(180deg, var(--yellow), rgba(184, 110, 30, 0.3)); }
.def-box.warning-box .def-label { color: var(--yellow); }

/* ── Quick-Check Inline Quiz ── */
.quick-check {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem 1.75rem;
  margin: 1.75rem 0;
  box-shadow: 0 2px 16px rgba(var(--shadow-card-rgb), 0.05);
  position: relative;
  overflow: hidden;
}
.quick-check::after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--accent), var(--purple));
  opacity: 0.6;
}
.quick-check .qc-question {
  font-weight: 700;
  margin-bottom: 1rem;
  font-size: 0.95rem;
  padding-top: 0.25rem;
}
.qc-options { display: flex; flex-direction: column; gap: 0.5rem; }
.qc-opt {
  padding: 0.65rem 1.15rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 0.875rem;
  transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
  position: relative;
  overflow: hidden;
}
.qc-opt::before {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(var(--accent-rgb), 0.06), transparent);
  opacity: 0;
  transition: opacity 0.25s;
}
.qc-opt:hover {
  border-color: rgba(var(--accent-rgb), 0.5);
  transform: translateX(4px);
}
.qc-opt:hover::before { opacity: 1; }
.qc-opt.chosen { pointer-events: none; }
.qc-opt.right {
  border-color: var(--green);
  background: var(--green-bg);
  color: var(--green);
  font-weight: 600;
}
.qc-opt.not-right {
  border-color: var(--red);
  background: var(--red-bg);
  color: var(--red);
  opacity: 0.65;
}
.qc-feedback {
  margin-top: 1rem;
  padding: 0.85rem 1.15rem;
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  display: none;
  line-height: 1.5;
  font-weight: 500;
}
.qc-feedback.show { display: block; animation: fadeSlideIn 0.3s ease; }
.qc-feedback.correct-fb {
  background: var(--green-bg);
  color: var(--green);
  border: 1px solid rgba(22, 128, 91, 0.25);
}
.qc-feedback.wrong-fb {
  background: var(--red-bg);
  color: var(--red);
  border: 1px solid rgba(194, 65, 12, 0.25);
}

@keyframes fadeSlideIn {
  from { opacity: 0; transform: translateY(-6px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ── Responsive ── */
@media (max-width: 900px) {
  .toc-sidebar { display: none; }
  .math-content { margin-left: 0; }
  .math-content .section { padding: 1.5rem 1.25rem; }
  .back-bar { padding: 0.6rem 1rem; }
}