/* ============================================================
   FTECA 24 · SUBJECT DETAIL DESIGN SYSTEM (sd2)
   Scoped design system for #page-subject-detail + global
   sidebar/header polish. Reuses global tokens from style.css.
   ============================================================ */

/* ─── 1. ACCENT TINTS ─────────────────────────────────────── */
.sd2-tint-green  { background: rgba(0, 185, 107, 0.12); color: #00a05c; }
.sd2-tint-blue   { background: rgba(59, 130, 246, 0.12); color: #3b82f6; }
.sd2-tint-orange { background: rgba(245, 158, 11, 0.14); color: #d97706; }
.sd2-tint-purple { background: rgba(139, 92, 246, 0.12); color: #8b5cf6; }
.sd2-tint-pink   { background: rgba(236, 72, 153, 0.12); color: #ec4899; }
.sd2-tint-cyan   { background: rgba(6, 182, 212, 0.12); color: #0891b2; }

[data-theme="dark"] .sd2-tint-green  { background: rgba(0, 217, 126, 0.15); color: #3ce68f; }
[data-theme="dark"] .sd2-tint-blue   { background: rgba(96, 165, 250, 0.16); color: #7db2ff; }
[data-theme="dark"] .sd2-tint-orange { background: rgba(251, 191, 36, 0.15); color: #fbbf24; }
[data-theme="dark"] .sd2-tint-purple { background: rgba(167, 139, 250, 0.16); color: #b79dfd; }
[data-theme="dark"] .sd2-tint-pink   { background: rgba(244, 114, 182, 0.16); color: #f472b6; }
[data-theme="dark"] .sd2-tint-cyan   { background: rgba(34, 211, 238, 0.15); color: #22d3ee; }

/* ─── 2. SHELL & BACK BUTTON ──────────────────────────────── */
.sd2-shell {
  max-width: 1440px;
  margin: 0 auto;
  padding: 24px clamp(16px, 2.4vw, 34px) 56px;
  display: flex;
  flex-direction: column;
  gap: 22px;
  animation: sd2FadeUp 0.35s ease both;
}
@keyframes sd2FadeUp {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: none; }
}

.sd2-back {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  align-self: flex-start;
  padding: 10px 18px;
  border: 1px solid var(--border);
  border-radius: var(--radius-full);
  background: var(--bg-card);
  color: var(--text-primary);
  font-size: 13.5px;
  font-weight: 700;
  box-shadow: var(--shadow-xs);
  transition: var(--transition);
}
.sd2-back i { font-size: 12px; color: var(--primary); transition: transform 0.2s ease; }
.sd2-back:hover { transform: translateY(-2px); border-color: color-mix(in srgb, var(--primary) 40%, var(--border)); box-shadow: var(--shadow-sm); }
.sd2-back:hover i { transform: translateX(-2px); }

/* ─── 3. HERO ─────────────────────────────────────────────── */
.sd2-hero {
  position: relative;
  isolation: isolate;
  overflow: hidden;
  display: flex;
  align-items: center;
  min-height: 330px;
  padding: 46px 48px;
  border: 1px solid var(--border);
  border-radius: 26px;
  background: linear-gradient(118deg, var(--bg-card) 34%, color-mix(in srgb, var(--theme-soft, #dff8eb) 80%, var(--bg-card)) 100%);
  box-shadow: var(--shadow-sm);
}
.sd2-hero-decor { position: absolute; inset: 0; z-index: 0; pointer-events: none; }
.sd2-orb { position: absolute; border-radius: 50%; }
.sd2-orb-one {
  width: 340px; height: 340px; right: -70px; top: -140px;
  background: radial-gradient(circle at 35% 35%, color-mix(in srgb, var(--theme-main, #00b96b) 16%, transparent), transparent 68%);
}
.sd2-orb-two {
  width: 260px; height: 260px; left: 32%; bottom: -170px;
  background: radial-gradient(circle at 50% 40%, color-mix(in srgb, var(--theme-main, #00b96b) 10%, transparent), transparent 70%);
}
.sd2-dots {
  position: absolute; right: 30%; top: 26px; width: 150px; height: 90px;
  background-image: radial-gradient(color-mix(in srgb, var(--theme-main, #00b96b) 30%, transparent) 1.5px, transparent 1.5px);
  background-size: 15px 15px;
  opacity: 0.55;
  mask-image: radial-gradient(circle at 60% 40%, #000 30%, transparent 78%);
  -webkit-mask-image: radial-gradient(circle at 60% 40%, #000 30%, transparent 78%);
}

.sd2-hero-copy { position: relative; z-index: 2; max-width: 660px; }
.sd2-badge {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 8px 14px;
  border-radius: var(--radius-full);
  background: color-mix(in srgb, var(--theme-main, #00b96b) 13%, var(--bg-card));
  color: var(--theme-main, #00a05c);
  font-size: 11.5px; font-weight: 800; letter-spacing: 0.06em;
  box-shadow: inset 0 0 0 1px color-mix(in srgb, var(--theme-main, #00b96b) 22%, transparent);
}
.sd2-badge-dot { width: 7px; height: 7px; border-radius: 50%; background: var(--theme-main, #00b96b); box-shadow: 0 0 0 3px color-mix(in srgb, var(--theme-main, #00b96b) 20%, transparent); }
.sd2-title {
  margin: 18px 0 10px;
  font-size: clamp(32px, 3.4vw, 44px);
  font-weight: 800;
  line-height: 1.12;
  letter-spacing: -0.035em;
  color: var(--text-primary);
}
.sd2-desc { margin: 0 0 20px; max-width: 620px; font-size: 15.5px; line-height: 1.7; color: var(--text-secondary); }
.sd2-meta { display: flex; flex-wrap: wrap; gap: 10px; }
.sd2-meta-chip {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 8px 14px;
  border: 1px solid var(--border);
  border-radius: var(--radius-full);
  background: color-mix(in srgb, var(--bg-card) 82%, transparent);
  backdrop-filter: blur(4px);
  font-size: 12.5px; font-weight: 700; color: var(--text-primary);
  box-shadow: var(--shadow-xs);
}
.sd2-meta-chip i { color: var(--theme-main, #00b96b); font-size: 12px; }
.sd2-cta { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 24px; }
.sd2-btn-primary {
  display: inline-flex; align-items: center; gap: 9px;
  padding: 12px 22px;
  border-radius: var(--radius-full);
  background: var(--primary);
  color: var(--text-on-primary, #fff);
  font-size: 13.5px; font-weight: 800;
  box-shadow: 0 6px 18px var(--primary-glow);
  transition: var(--transition);
}
.sd2-btn-primary:hover { transform: translateY(-2px); background: var(--primary-hover); box-shadow: 0 10px 24px var(--primary-glow); }
.sd2-btn-ghost {
  display: inline-flex; align-items: center; gap: 9px;
  padding: 12px 20px;
  border: 1px solid var(--border);
  border-radius: var(--radius-full);
  background: color-mix(in srgb, var(--bg-card) 86%, transparent);
  color: var(--text-primary);
  font-size: 13.5px; font-weight: 700;
  transition: var(--transition);
}
.sd2-btn-ghost i { color: var(--primary); }
.sd2-btn-ghost:hover { transform: translateY(-2px); border-color: color-mix(in srgb, var(--primary) 40%, var(--border)); box-shadow: var(--shadow-sm); }

.sd2-hero-art { position: absolute; z-index: 1; right: 26px; top: 0; bottom: 0; width: 360px; pointer-events: none; }
.sd2-art-ring { position: absolute; border-radius: 50%; border: 1.5px solid color-mix(in srgb, var(--theme-main, #00b96b) 26%, transparent); }
.sd2-art-ring-one { width: 300px; height: 300px; right: 10px; top: 50%; transform: translateY(-50%); }
.sd2-art-ring-two { width: 218px; height: 218px; right: 52px; top: 50%; transform: translateY(-50%); border-style: dashed; opacity: 0.7; }
.sd2-art-platform {
  position: absolute; right: 30px; bottom: 26px; width: 260px; height: 74px;
  border-radius: 50%;
  background: linear-gradient(180deg, color-mix(in srgb, var(--theme-main, #00b96b) 30%, transparent), color-mix(in srgb, var(--theme-main, #00b96b) 6%, transparent));
  filter: blur(1px);
}
.sd2-art-emblem {
  position: absolute; right: 96px; top: 50%; transform: translateY(-56%);
  display: grid; place-items: center;
  width: 128px; height: 128px;
  border-radius: 34px;
  background: linear-gradient(140deg, color-mix(in srgb, var(--bg-card) 92%, transparent), color-mix(in srgb, var(--theme-soft, #dff8eb) 90%, transparent));
  border: 1px solid color-mix(in srgb, var(--theme-main, #00b96b) 26%, transparent);
  box-shadow: 0 18px 38px color-mix(in srgb, var(--theme-main, #00b96b) 20%, transparent);
  color: var(--theme-main, #00b96b);
  font-size: 46px;
}
.sd2-art-float {
  position: absolute;
  display: grid; place-items: center;
  width: 46px; height: 46px;
  border-radius: 15px;
  background: color-mix(in srgb, var(--bg-card) 90%, transparent);
  border: 1px solid var(--border);
  box-shadow: var(--shadow-sm);
  color: var(--theme-main, #00b96b);
  font-size: 17px;
  animation: sd2Float 5.5s ease-in-out infinite alternate;
}
.sd2-art-float-one { right: 40px; top: 22%; }
.sd2-art-float-two { right: 250px; top: 62%; animation-delay: 1.4s; }
@keyframes sd2Float {
  from { transform: translateY(-5px); }
  to   { transform: translateY(7px); }
}

/* ─── 4. KEY STATS STRIP ──────────────────────────────────── */
.sd2-stats { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 16px; }
.sd2-stat {
  display: flex; align-items: center; gap: 14px;
  padding: 16px 18px;
  border: 1px solid var(--border);
  border-radius: 18px;
  background: var(--bg-card);
  box-shadow: var(--shadow-xs);
  transition: var(--transition);
}
.sd2-stat:hover { transform: translateY(-2px); box-shadow: var(--shadow-sm); }
.sd2-stat-icon { flex: none; display: grid; width: 42px; height: 42px; place-items: center; border-radius: 13px; font-size: 16px; }
.sd2-stat strong { display: block; font-size: 21px; font-weight: 800; letter-spacing: -0.02em; line-height: 1.15; color: var(--text-primary); }
.sd2-stat > div > span { display: block; font-size: 12px; font-weight: 600; color: var(--text-muted); }

/* ─── 5. MAIN GRID ────────────────────────────────────────── */
.sd2-grid { display: grid; grid-template-columns: minmax(0, 1fr) 360px; gap: 22px; align-items: start; }
.sd2-main { display: flex; flex-direction: column; gap: 20px; min-width: 0; }
.sd2-side { position: sticky; top: 76px; min-width: 0; }

.sd2-card {
  padding: 24px 26px;
  border: 1px solid var(--border);
  border-radius: 20px;
  background: var(--bg-card);
  box-shadow: var(--shadow-xs);
  transition: var(--transition);
}
.sd2-card-head { display: flex; align-items: center; gap: 14px; margin-bottom: 18px; }
.sd2-head-icon { flex: none; display: grid; width: 44px; height: 44px; place-items: center; border-radius: 14px; font-size: 17px; }
.sd2-card-title { margin: 0; font-size: 20px; font-weight: 800; letter-spacing: -0.02em; color: var(--text-primary); }
.sd2-card-sub { margin: 2px 0 0; font-size: 12.5px; font-weight: 600; color: var(--text-muted); }
.sd2-intro-text { margin: 0; font-size: 14.5px; line-height: 1.78; color: var(--text-secondary); }
.sd2-empty {
  display: flex; flex-direction: column; align-items: center; gap: 10px;
  padding: 30px 20px;
  border: 1.5px dashed color-mix(in srgb, var(--primary) 30%, var(--border));
  border-radius: 16px;
  background: color-mix(in srgb, var(--primary) 4%, transparent);
  color: var(--text-muted);
  font-size: 13px; font-weight: 600; font-style: italic;
  text-align: center;
}
.sd2-empty i { font-size: 20px; color: color-mix(in srgb, var(--primary) 55%, var(--text-muted)); font-style: normal; }
.sd2-empty-sm { padding: 18px 14px; margin-top: 10px; border-radius: 13px; }

/* ─── 6. INFO CARDS 2×2 ───────────────────────────────────── */
.sd2-infogrid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; }
.sd2-info {
  padding: 20px 20px 22px;
  border: 1px solid var(--border);
  border-radius: 18px;
  background: var(--bg-card);
  box-shadow: var(--shadow-xs);
  transition: var(--transition);
}
.sd2-tint-card-green  { background: linear-gradient(150deg, color-mix(in srgb, #00b96b 6%, var(--bg-card)), var(--bg-card) 62%); }
.sd2-tint-card-blue   { background: linear-gradient(150deg, color-mix(in srgb, #3b82f6 6%, var(--bg-card)), var(--bg-card) 62%); }
.sd2-tint-card-orange { background: linear-gradient(150deg, color-mix(in srgb, #f59e0b 7%, var(--bg-card)), var(--bg-card) 62%); }
.sd2-tint-card-purple { background: linear-gradient(150deg, color-mix(in srgb, #8b5cf6 6%, var(--bg-card)), var(--bg-card) 62%); }
.sd2-info:hover { transform: translateY(-2px); box-shadow: var(--shadow-sm); border-color: color-mix(in srgb, var(--primary) 28%, var(--border)); }
.sd2-info-icon { display: grid; width: 42px; height: 42px; place-items: center; border-radius: 13px; font-size: 16px; }
.sd2-info h3 { margin: 13px 0 6px; font-size: 15px; font-weight: 700; color: var(--text-primary); }
.sd2-info p { margin: 0; font-size: 13px; line-height: 1.68; color: var(--text-secondary); }

/* ─── 7. INSTRUCTOR ───────────────────────────────────────── */
.sd2-instructor { display: flex; align-items: center; justify-content: space-between; gap: 18px; flex-wrap: wrap; }
.sd2-instructor-left { display: flex; align-items: center; gap: 14px; min-width: 0; }
.sd2-instructor-avatar { width: 54px; height: 54px; border-radius: 50%; object-fit: cover; border: 1px solid var(--border); }
.sd2-instructor-fallback { display: grid; width: 54px; height: 54px; place-items: center; border-radius: 50%; font-size: 20px; }
.sd2-instructor-name { margin: 0; font-size: 16px; font-weight: 800; color: var(--text-primary); }
.sd2-instructor-role { margin: 2px 0 0; font-size: 12.5px; font-weight: 600; color: var(--text-muted); }
.sd2-instructor-contact {
  display: inline-flex; align-items: center; gap: 9px;
  padding: 10px 16px;
  border-radius: var(--radius-full);
  background: color-mix(in srgb, var(--primary) 9%, transparent);
  color: var(--primary-hover);
  font-size: 13px; font-weight: 800;
  transition: var(--transition);
}
.sd2-instructor-contact i:last-child { font-size: 10px; transition: transform 0.2s ease; }
.sd2-instructor-contact:hover { background: color-mix(in srgb, var(--primary) 16%, transparent); transform: translateY(-1px); }
.sd2-instructor-contact:hover i:last-child { transform: translateX(2px); }
[data-theme="dark"] .sd2-instructor-contact { color: #3ce68f; }

/* ─── 8. TOC SIDEBAR ──────────────────────────────────────── */
.sd2-toc { padding: 18px 16px; }
.sd2-toc-head { display: flex; align-items: center; justify-content: space-between; gap: 10px; margin-bottom: 12px; padding: 0 4px; }
.sd2-toc-head h2 { display: flex; align-items: center; gap: 9px; margin: 0; font-size: 15px; font-weight: 800; letter-spacing: -0.01em; color: var(--text-primary); }
.sd2-toc-head h2 i { color: var(--primary); font-size: 14px; }
.sd2-toc-toggle {
  display: inline-flex; align-items: center; gap: 7px;
  padding: 6px 12px;
  border-radius: var(--radius-full);
  background: var(--bg-subtle);
  color: var(--text-secondary);
  font-size: 11.5px; font-weight: 700;
  transition: var(--transition);
}
.sd2-toc-toggle:hover { background: color-mix(in srgb, var(--primary) 10%, var(--bg-subtle)); color: var(--primary-hover); }
.sd2-toc-toggle > i:last-child { font-size: 10px; }

.sd2-toc-overview {
  display: flex; align-items: center; gap: 10px;
  width: 100%;
  padding: 11px 14px;
  border-radius: 13px;
  background: color-mix(in srgb, var(--primary) 10%, transparent);
  color: var(--primary-hover);
  font-size: 13.5px; font-weight: 800;
  text-align: left;
  transition: var(--transition);
}
.sd2-toc-overview .sd2-chev { margin-left: auto; font-size: 10px; opacity: 0.7; transition: transform 0.2s ease; }
.sd2-toc-overview:hover { background: color-mix(in srgb, var(--primary) 16%, transparent); }
.sd2-toc-overview:hover .sd2-chev { transform: translateX(2px); }
[data-theme="dark"] .sd2-toc-overview { color: #3ce68f; }

.sd2-toc-chapters { display: flex; flex-direction: column; gap: 4px; margin-top: 12px; }
.sd2-chap-head {
  display: flex; align-items: center; gap: 10px;
  width: 100%;
  padding: 9px 10px;
  border-radius: 12px;
  color: var(--text-primary);
  text-align: left;
  transition: var(--transition);
}
.sd2-chap-head:hover { background: var(--bg-subtle); }
.sd2-chap-idx {
  flex: none;
  display: grid; place-items: center;
  width: 27px; height: 27px;
  border-radius: 9px;
  background: color-mix(in srgb, var(--primary) 11%, transparent);
  color: var(--primary-hover);
  font-size: 11px; font-weight: 800;
}
[data-theme="dark"] .sd2-chap-idx { color: #3ce68f; }
.sd2-chap-title { flex: 1; min-width: 0; font-size: 13px; font-weight: 700; line-height: 1.45; }
.sd2-chap-head .toc-chap-arrow { color: var(--text-muted); font-size: 10px; transition: transform 0.2s ease; }

.sd2-lessons {
  display: flex; flex-direction: column; gap: 2px;
  margin: 2px 0 8px 23px;
  padding-left: 15px;
  border-left: 1.5px solid color-mix(in srgb, var(--primary) 22%, var(--border));
}
.sd2-lesson {
  display: flex; align-items: center; gap: 10px;
  width: 100%;
  padding: 8px 10px;
  border-radius: 10px;
  color: var(--text-secondary);
  font-size: 12.5px; font-weight: 600; line-height: 1.5;
  text-align: left;
  transition: var(--transition);
}
.sd2-lesson:hover { background: var(--bg-subtle); color: var(--text-primary); }
.sd2-lesson-dot { flex: none; width: 6px; height: 6px; border-radius: 50%; background: color-mix(in srgb, var(--text-muted) 55%, transparent); transition: var(--transition); }
.sd2-lesson.active {
  background: color-mix(in srgb, var(--primary) 12%, transparent);
  color: var(--primary-hover);
  font-weight: 700;
}
.sd2-lesson.active .sd2-lesson-dot { background: var(--primary); box-shadow: 0 0 0 3px color-mix(in srgb, var(--primary) 18%, transparent); }
[data-theme="dark"] .sd2-lesson.active { color: #3ce68f; }

/* ─── 9. EXPLORE GRID ─────────────────────────────────────── */
.sd2-section-head { margin-bottom: 14px; }
.sd2-section-head h2 { margin: 0; font-size: 22px; font-weight: 800; letter-spacing: -0.02em; color: var(--text-primary); }
.sd2-section-head p { margin: 4px 0 0; font-size: 13px; font-weight: 600; color: var(--text-muted); }
.sd2-explore-grid { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 16px; }
.sd2-explore-card {
  display: flex; flex-direction: column; align-items: flex-start; gap: 10px;
  padding: 20px;
  border: 1px solid var(--border);
  border-radius: 18px;
  background: var(--bg-card);
  box-shadow: var(--shadow-xs);
  text-align: left;
  transition: var(--transition);
}
.sd2-explore-card:hover {
  transform: translateY(-3px);
  border-color: color-mix(in srgb, var(--primary) 34%, var(--border));
  box-shadow: var(--shadow-md);
}
.sd2-explore-icon { display: grid; width: 44px; height: 44px; place-items: center; border-radius: 14px; font-size: 17px; }
.sd2-explore-name { font-size: 15px; font-weight: 700; color: var(--text-primary); }
.sd2-explore-desc { font-size: 12.5px; line-height: 1.6; color: var(--text-muted); }
.sd2-explore-open {
  display: inline-flex; align-items: center; gap: 7px;
  margin-top: auto; padding-top: 6px;
  color: var(--primary-hover);
  font-size: 12.5px; font-weight: 800;
}
.sd2-explore-open i { font-size: 11px; transition: transform 0.2s ease; }
.sd2-explore-card:hover .sd2-explore-open i { transform: translateX(3px); }
[data-theme="dark"] .sd2-explore-open { color: #3ce68f; }

/* ─── 10. DARK MODE ───────────────────────────────────────── */
[data-theme="dark"] .sd2-hero {
  background:
    radial-gradient(circle at 82% 12%, color-mix(in srgb, var(--theme-main, #00b96b) 16%, transparent), transparent 46%),
    linear-gradient(118deg, var(--bg-card) 30%, color-mix(in srgb, var(--theme-main, #00b96b) 10%, var(--bg-card)) 100%);
}
[data-theme="dark"] .sd2-badge {
  background: color-mix(in srgb, var(--theme-main, #00b96b) 20%, transparent);
  color: color-mix(in srgb, var(--theme-main, #00b96b) 62%, #ffffff);
}
[data-theme="dark"] .sd2-meta-chip { background: rgba(255, 255, 255, 0.05); border-color: rgba(255, 255, 255, 0.12); }
[data-theme="dark"] .sd2-btn-ghost { background: rgba(255, 255, 255, 0.05); border-color: rgba(255, 255, 255, 0.14); }
[data-theme="dark"] .sd2-card,
[data-theme="dark"] .sd2-stat,
[data-theme="dark"] .sd2-info,
[data-theme="dark"] .sd2-explore-card { box-shadow: 0 6px 20px rgba(0, 0, 0, 0.35); }
[data-theme="dark"] .sd2-tint-card-green,
[data-theme="dark"] .sd2-tint-card-blue,
[data-theme="dark"] .sd2-tint-card-orange,
[data-theme="dark"] .sd2-tint-card-purple { background: var(--bg-card); }
[data-theme="dark"] .sd2-art-emblem { background: linear-gradient(140deg, rgba(255, 255, 255, 0.10), color-mix(in srgb, var(--theme-main, #00b96b) 24%, transparent)); }
[data-theme="dark"] .sd2-art-float { background: rgba(255, 255, 255, 0.07); border-color: rgba(255, 255, 255, 0.12); }
[data-theme="dark"] .sd2-empty { background: color-mix(in srgb, var(--primary) 7%, transparent); }
[data-theme="dark"] .sd2-toc-toggle { background: rgba(255, 255, 255, 0.07); color: var(--text-secondary); }

/* ─── 11. RESPONSIVE ──────────────────────────────────────── */
@media (max-width: 1280px) {
  .sd2-grid { grid-template-columns: minmax(0, 1fr) 320px; }
  .sd2-explore-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 1080px) {
  .sd2-hero-art { display: none; }
  .sd2-hero { min-height: 0; padding: 36px 34px; }
}
@media (max-width: 992px) {
  .sd2-grid { grid-template-columns: 1fr; }
  .sd2-side { position: static; order: -1; }
  .sd2-stats { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 640px) {
  .sd2-shell { padding: 16px 14px 40px; gap: 16px; }
  .sd2-hero { padding: 28px 22px; border-radius: 20px; }
  .sd2-title { font-size: 30px; }
  .sd2-card { padding: 18px 16px; border-radius: 18px; }
  .sd2-infogrid { grid-template-columns: 1fr; }
  .sd2-explore-grid { grid-template-columns: 1fr; }
  .sd2-instructor { flex-direction: column; align-items: flex-start; }
}
@media (max-width: 480px) {
  .sd2-stats { grid-template-columns: 1fr; }
}

/* ============================================================
   12. GLOBAL SHELL POLISH (sidebar + header)
   Đồng bộ toàn hệ thống, không đổi cấu trúc.
   ============================================================ */
.sidebar-nav-group { gap: 4px; }
.sidebar-nav-item {
  padding: 10px 12px;
  border-radius: 12px;
  font-weight: 600;
}
.sidebar-nav-item.active {
  box-shadow: inset 0 0 0 1px color-mix(in srgb, var(--primary) 24%, transparent);
}
.sidebar-divider {
  padding: 16px 12px 6px;
  font-size: 10px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}
.subject-search-input {
  height: 40px;
  border-radius: var(--radius-full);
  background: var(--bg-card);
  box-shadow: var(--shadow-xs);
}
.subject-search-input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-glow);
}
.btn-icon {
  border-radius: 12px;
  background: var(--bg-card);
  box-shadow: var(--shadow-xs);
  transition: var(--transition);
}
.btn-icon:hover { transform: translateY(-1px); box-shadow: var(--shadow-sm); }
.user-avatar-btn {
  background: var(--bg-card);
  padding: 4px 12px 4px 4px;
  box-shadow: var(--shadow-xs);
  transition: var(--transition);
}
.user-avatar-btn:hover { transform: translateY(-1px); box-shadow: var(--shadow-sm); }