/* ============================================================
   SELECTION GUIDE — Dedicated Stylesheet
   Inherits: shared.css (site-header, footer, btn, container, etc.)
   ============================================================ */

/* ---- HERO ---- */
.sg-hero {
  position: relative;
  min-height: 560px;
  display: flex;
  align-items: flex-end;
  padding-bottom: 72px;
  overflow: hidden;
}
.sg-hero-bg {
  position: absolute;
  inset: 0;
  background-size: cover;
  background-position: center 30%;
  transform: scale(1.04);
}
.sg-hero-overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(5,20,50,0.88) 0%, rgba(10,40,90,0.72) 60%, rgba(0,80,160,0.40) 100%);
}
.sg-hero-content {
  position: relative;
  z-index: 2;
  max-width: 760px;
}
.sg-breadcrumb {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.82rem;
  color: rgba(255,255,255,0.65);
  margin-bottom: 16px;
}
.sg-breadcrumb a {
  color: rgba(255,255,255,0.65);
  text-decoration: none;
  transition: color 0.2s;
}
.sg-breadcrumb a:hover { color: #fff; }
.sg-hero-title {
  font-size: clamp(2.2rem, 5vw, 3.6rem);
  font-weight: 900;
  color: #fff;
  line-height: 1.1;
  margin: 12px 0 20px;
  letter-spacing: -0.02em;
}
.sg-hero-desc {
  font-size: 1.05rem;
  color: rgba(255,255,255,0.82);
  line-height: 1.7;
  margin-bottom: 24px;
  max-width: 640px;
}
.sg-hero-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-bottom: 32px;
}
.sg-hero-meta span {
  background: rgba(255,255,255,0.12);
  border: 1px solid rgba(255,255,255,0.22);
  color: rgba(255,255,255,0.88);
  padding: 5px 14px;
  border-radius: 20px;
  font-size: 0.82rem;
  font-weight: 500;
}
.sg-hero-cta {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
}

/* ---- CHAPTER NAV ---- */
.chapter-nav {
  background: #0a1628;
  border-bottom: 1px solid rgba(255,255,255,0.08);
  z-index: 90;
  transition: box-shadow 0.3s;
}
.chapter-nav.sticky {
  position: sticky;
  top: 64px;
  box-shadow: 0 4px 24px rgba(0,0,0,0.3);
}
.chapter-nav-inner {
  display: flex;
  align-items: center;
  overflow-x: auto;
  gap: 0;
  scrollbar-width: none;
}
.chapter-nav-inner::-webkit-scrollbar { display: none; }
.ch-link {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 16px 20px;
  color: rgba(255,255,255,0.55);
  text-decoration: none;
  font-size: 0.82rem;
  font-weight: 500;
  white-space: nowrap;
  border-bottom: 2px solid transparent;
  transition: color 0.2s, border-color 0.2s;
}
.ch-link:hover { color: rgba(255,255,255,0.9); }
.ch-link.active {
  color: #4da8ff;
  border-bottom-color: #4da8ff;
}
.ch-num {
  font-size: 0.72rem;
  font-weight: 700;
  color: rgba(255,255,255,0.3);
  font-family: monospace;
}
.ch-link.active .ch-num { color: #4da8ff; }

/* ---- CHAPTERS ---- */
.sg-chapter {
  padding: 96px 0;
  background: #060f22;
}
.sg-chapter-alt {
  background: #081428;
}
.chapter-header {
  display: flex;
  align-items: flex-start;
  gap: 28px;
  margin-bottom: 56px;
}
.chapter-num-badge {
  flex-shrink: 0;
  width: 64px;
  height: 64px;
  background: linear-gradient(135deg, #1a4fa0, #0a2d6e);
  border-radius: 16px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.4rem;
  font-weight: 900;
  color: rgba(255,255,255,0.7);
  font-family: monospace;
  border: 1px solid rgba(77,168,255,0.2);
}
.chapter-title {
  font-size: clamp(1.7rem, 3vw, 2.4rem);
  font-weight: 800;
  color: #fff;
  margin: 8px 0 14px;
  line-height: 1.2;
}
.chapter-intro {
  font-size: 1.05rem;
  color: rgba(255,255,255,0.65);
  line-height: 1.75;
  max-width: 680px;
}

/* ---- TWO-COLUMN LAYOUT ---- */
.sg-two-col {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 56px;
  align-items: start;
}
.sg-two-col-reverse { direction: rtl; }
.sg-two-col-reverse > * { direction: ltr; }
.sg-two-col-narrow {
  grid-template-columns: 1fr 1.4fr;
}
.sg-text-col h3 {
  font-size: 1.25rem;
  font-weight: 700;
  color: #fff;
  margin: 0 0 16px;
}
.sg-text-col p {
  color: rgba(255,255,255,0.72);
  line-height: 1.75;
  margin-bottom: 20px;
}
.sg-figure {
  margin: 0;
  border-radius: 16px;
  overflow: hidden;
  border: 1px solid rgba(255,255,255,0.08);
}
.sg-figure img {
  width: 100%;
  height: 280px;
  object-fit: cover;
  display: block;
}
.sg-figure figcaption {
  padding: 14px 18px;
  font-size: 0.8rem;
  color: rgba(255,255,255,0.45);
  background: rgba(255,255,255,0.04);
  line-height: 1.5;
}

/* ---- KEY RULE BOX ---- */
.key-rule {
  display: flex;
  gap: 16px;
  background: linear-gradient(135deg, rgba(77,168,255,0.08), rgba(0,80,160,0.12));
  border: 1px solid rgba(77,168,255,0.25);
  border-radius: 12px;
  padding: 20px 22px;
  margin: 24px 0;
}
.key-rule-icon {
  font-size: 1.6rem;
  flex-shrink: 0;
  line-height: 1;
  margin-top: 2px;
}
.key-rule strong {
  display: block;
  color: #4da8ff;
  font-size: 0.95rem;
  margin-bottom: 6px;
}
.key-rule p {
  margin: 0;
  font-size: 0.9rem;
}

/* ---- VOLTAGE LEVELS ---- */
.voltage-levels {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-top: 8px;
}
.vl-item {
  display: flex;
  gap: 16px;
  align-items: flex-start;
  background: rgba(255,255,255,0.04);
  border-radius: 12px;
  padding: 16px 18px;
  border-left: 3px solid;
}
.vl-lv { border-color: #22c55e; }
.vl-mv { border-color: #f59e0b; }
.vl-hv { border-color: #ef4444; }
.vl-badge {
  flex-shrink: 0;
  width: 40px;
  height: 40px;
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.05em;
}
.vl-lv .vl-badge { background: rgba(34,197,94,0.15); color: #22c55e; }
.vl-mv .vl-badge { background: rgba(245,158,11,0.15); color: #f59e0b; }
.vl-hv .vl-badge { background: rgba(239,68,68,0.15); color: #ef4444; }
.vl-content strong {
  display: block;
  color: #fff;
  font-size: 0.95rem;
  margin-bottom: 2px;
}
.vl-range {
  font-size: 0.78rem;
  color: rgba(255,255,255,0.45);
  font-family: monospace;
  display: block;
  margin-bottom: 6px;
}
.vl-content p {
  font-size: 0.85rem;
  color: rgba(255,255,255,0.6);
  margin: 0 0 10px;
  line-height: 1.55;
}
.vl-apps {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}
.vl-apps span {
  font-size: 0.72rem;
  background: rgba(255,255,255,0.07);
  color: rgba(255,255,255,0.55);
  padding: 3px 10px;
  border-radius: 12px;
}

/* ---- VOLTAGE FLOW ---- */
.sg-visual-module {
  background: rgba(255,255,255,0.03);
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 16px;
  padding: 24px;
  margin-top: 20px;
}
.vm-title {
  font-size: 0.88rem;
  font-weight: 600;
  color: rgba(255,255,255,0.55);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin: 0 0 20px;
}
.voltage-flow {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
  justify-content: center;
}
.vf-step {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
  background: rgba(255,255,255,0.05);
  border-radius: 12px;
  padding: 14px 16px;
  min-width: 80px;
  text-align: center;
  border: 1px solid rgba(255,255,255,0.08);
}
.vf-mv { border-color: rgba(245,158,11,0.3); background: rgba(245,158,11,0.06); }
.vf-tx { border-color: rgba(77,168,255,0.3); background: rgba(77,168,255,0.06); }
.vf-lv { border-color: rgba(34,197,94,0.3); background: rgba(34,197,94,0.06); }
.vf-icon { font-size: 1.4rem; }
.vf-label { font-size: 0.78rem; font-weight: 600; color: #fff; }
.vf-sub { font-size: 0.68rem; color: rgba(255,255,255,0.45); font-family: monospace; }
.vf-arrow {
  font-size: 1.2rem;
  color: rgba(255,255,255,0.3);
  flex-shrink: 0;
}

/* ---- SCENARIO CARDS ---- */
.scenario-cards {
  display: flex;
  flex-direction: column;
  gap: 14px;
}
.sc-card {
  display: flex;
  gap: 16px;
  background: rgba(255,255,255,0.04);
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 12px;
  padding: 18px 20px;
  transition: border-color 0.2s;
}
.sc-card:hover { border-color: rgba(77,168,255,0.3); }
.sc-icon { font-size: 1.6rem; flex-shrink: 0; line-height: 1; margin-top: 2px; }
.sc-header {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 8px;
}
.sc-header strong {
  color: #fff;
  font-size: 0.95rem;
}
.sc-badge {
  font-size: 0.7rem;
  font-weight: 600;
  padding: 3px 10px;
  border-radius: 10px;
  letter-spacing: 0.03em;
}
.sc-lszh { background: rgba(77,168,255,0.15); color: #4da8ff; }
.sc-fire { background: rgba(239,68,68,0.15); color: #ef4444; }
.sc-armored { background: rgba(245,158,11,0.15); color: #f59e0b; }
.sc-pv { background: rgba(234,179,8,0.15); color: #eab308; }
.sc-mining { background: rgba(168,85,247,0.15); color: #a855f7; }
.sc-atex { background: rgba(249,115,22,0.15); color: #f97316; }
.sc-content p {
  font-size: 0.85rem;
  color: rgba(255,255,255,0.6);
  line-height: 1.6;
  margin: 0;
}

/* ---- ENVIRONMENT MATRIX ---- */
.env-matrix {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
  margin-bottom: 56px;
}
.env-factor {
  background: rgba(255,255,255,0.03);
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 16px;
  overflow: hidden;
}
.env-factor-header {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 20px 22px 16px;
  border-bottom: 1px solid rgba(255,255,255,0.06);
}
.env-factor-icon { font-size: 1.6rem; }
.env-factor-header h3 {
  font-size: 1.05rem;
  font-weight: 700;
  color: #fff;
  margin: 0;
}
.env-factor-body { padding: 20px 22px; }
.env-factor-body > p {
  font-size: 0.88rem;
  color: rgba(255,255,255,0.6);
  line-height: 1.65;
  margin-bottom: 16px;
}
.env-comparison {
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.env-comp-item {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 12px;
  padding: 10px 14px;
  background: rgba(255,255,255,0.04);
  border-radius: 8px;
  font-size: 0.82rem;
}
.env-comp-label {
  color: rgba(255,255,255,0.55);
  flex-shrink: 0;
  max-width: 45%;
}
.env-comp-value {
  color: rgba(255,255,255,0.85);
  text-align: right;
  font-weight: 500;
}

/* ---- DERATING TABLE ---- */
.derate-table {
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 12px;
  overflow: hidden;
  margin: 20px 0;
}
.dt-header {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 16px;
  padding: 12px 18px;
  background: rgba(77,168,255,0.08);
  font-size: 0.78rem;
  font-weight: 700;
  color: rgba(255,255,255,0.55);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}
.dt-row {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 16px;
  padding: 12px 18px;
  border-top: 1px solid rgba(255,255,255,0.05);
  align-items: center;
  font-size: 0.88rem;
  color: rgba(255,255,255,0.72);
}
.dt-factor {
  font-family: monospace;
  font-weight: 700;
  font-size: 0.9rem;
  white-space: nowrap;
}
.dt-good { color: #22c55e; }
.dt-warn { color: #f59e0b; }
.dt-bad { color: #ef4444; }
.dt-note {
  font-size: 0.82rem;
  color: rgba(255,255,255,0.45);
  line-height: 1.55;
  margin-top: 12px;
}

/* ---- SIZING CRITERIA ---- */
.sizing-criteria {
  display: flex;
  flex-direction: column;
  gap: 24px;
  margin-bottom: 56px;
}
.sc-criterion {
  display: flex;
  gap: 24px;
  background: rgba(255,255,255,0.03);
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 16px;
  padding: 28px 30px;
}
.sc-crit-num {
  flex-shrink: 0;
  width: 44px;
  height: 44px;
  background: linear-gradient(135deg, #1a4fa0, #0a2d6e);
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  font-weight: 900;
  color: #4da8ff;
  font-family: monospace;
}
.sc-crit-content h3 {
  font-size: 1.05rem;
  font-weight: 700;
  color: #fff;
  margin: 0 0 10px;
}
.sc-crit-content p {
  font-size: 0.9rem;
  color: rgba(255,255,255,0.65);
  line-height: 1.7;
  margin-bottom: 16px;
}
.crit-formula {
  background: rgba(0,0,0,0.25);
  border: 1px solid rgba(77,168,255,0.2);
  border-radius: 10px;
  padding: 14px 18px;
}
.formula-text {
  display: block;
  font-family: 'Courier New', monospace;
  font-size: 1rem;
  color: #4da8ff;
  margin-bottom: 8px;
  font-weight: 600;
}
.formula-note {
  font-size: 0.78rem;
  color: rgba(255,255,255,0.45);
  line-height: 1.5;
}

/* ---- CONDUCTOR COMPARE ---- */
.conductor-compare {
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 12px;
  overflow: hidden;
  margin-top: 16px;
}
.cc-header, .cc-row {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr;
  gap: 0;
}
.cc-header {
  background: rgba(77,168,255,0.08);
  padding: 12px 16px;
  font-size: 0.78rem;
  font-weight: 700;
  color: rgba(255,255,255,0.55);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}
.cc-header span:nth-child(2) { color: #f59e0b; }
.cc-header span:nth-child(3) { color: #94a3b8; }
.cc-row {
  padding: 11px 16px;
  border-top: 1px solid rgba(255,255,255,0.05);
  font-size: 0.85rem;
  align-items: center;
}
.cc-row span:first-child { color: rgba(255,255,255,0.55); font-size: 0.82rem; }
.cc-good { color: #22c55e; font-weight: 600; }
.cc-ok { color: rgba(255,255,255,0.72); }
.cc-bad { color: #ef4444; font-weight: 600; }
.cc-warn { color: #f59e0b; }

/* ---- STANDARDS GRID ---- */
.standards-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
  margin-bottom: 32px;
}
.std-card {
  background: rgba(255,255,255,0.03);
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 16px;
  padding: 28px 28px 24px;
  transition: border-color 0.2s;
}
.std-card:hover { border-color: rgba(77,168,255,0.3); }
.std-logo {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 52px;
  height: 52px;
  border-radius: 12px;
  font-size: 1.1rem;
  font-weight: 900;
  letter-spacing: -0.02em;
  margin-bottom: 16px;
}
.std-iec { background: rgba(77,168,255,0.15); color: #4da8ff; }
.std-ul { background: rgba(239,68,68,0.15); color: #ef4444; }
.std-bs { background: rgba(34,197,94,0.15); color: #22c55e; }
.std-gb { background: rgba(245,158,11,0.15); color: #f59e0b; }
.std-card h3 {
  font-size: 1.05rem;
  font-weight: 700;
  color: #fff;
  margin: 0 0 8px;
}
.std-card > p {
  font-size: 0.85rem;
  color: rgba(255,255,255,0.55);
  line-height: 1.6;
  margin-bottom: 18px;
}
.std-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.std-list li {
  font-size: 0.83rem;
  color: rgba(255,255,255,0.65);
  padding: 8px 12px;
  background: rgba(255,255,255,0.04);
  border-radius: 8px;
  line-height: 1.45;
}
.std-list li strong {
  color: rgba(255,255,255,0.9);
  font-family: monospace;
  margin-right: 6px;
}
.std-note-box {
  display: flex;
  gap: 16px;
  background: rgba(245,158,11,0.06);
  border: 1px solid rgba(245,158,11,0.25);
  border-radius: 12px;
  padding: 20px 22px;
}
.std-note-icon { font-size: 1.4rem; flex-shrink: 0; }
.std-note-box strong {
  display: block;
  color: #f59e0b;
  margin-bottom: 6px;
  font-size: 0.95rem;
}
.std-note-box p {
  font-size: 0.88rem;
  color: rgba(255,255,255,0.65);
  line-height: 1.65;
  margin: 0;
}

/* ---- PITFALLS ---- */
.pitfalls-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}
.pitfall-card {
  background: rgba(255,255,255,0.03);
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 16px;
  padding: 24px 24px 20px;
  position: relative;
  transition: border-color 0.2s;
}
.pitfall-card:hover { border-color: rgba(255,255,255,0.18); }
.pitfall-danger { border-left: 3px solid #ef4444; }
.pitfall-high { border-left: 3px solid #f59e0b; }
.pitfall-medium { border-left: 3px solid #3b82f6; }
.pitfall-severity {
  font-size: 0.68rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: 10px;
}
.pitfall-danger .pitfall-severity { color: #ef4444; }
.pitfall-high .pitfall-severity { color: #f59e0b; }
.pitfall-medium .pitfall-severity { color: #3b82f6; }
.pitfall-icon { font-size: 1.8rem; margin-bottom: 10px; }
.pitfall-card h3 {
  font-size: 1rem;
  font-weight: 700;
  color: #fff;
  margin: 0 0 10px;
  line-height: 1.3;
}
.pitfall-card > p {
  font-size: 0.85rem;
  color: rgba(255,255,255,0.62);
  line-height: 1.65;
  margin-bottom: 16px;
}
.pitfall-prevention {
  background: rgba(255,255,255,0.04);
  border-radius: 8px;
  padding: 12px 14px;
  font-size: 0.82rem;
  color: rgba(255,255,255,0.6);
  line-height: 1.55;
}
.pitfall-prevention strong {
  color: rgba(255,255,255,0.85);
  display: block;
  margin-bottom: 4px;
}

/* ---- CTA SECTION ---- */
.sg-cta {
  background: linear-gradient(135deg, #0a2d6e 0%, #1a4fa0 50%, #0a2d6e 100%);
  padding: 96px 0;
}
.sg-cta-inner {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 56px;
  align-items: center;
}
.sg-cta-text h2 {
  font-size: clamp(1.7rem, 3vw, 2.4rem);
  font-weight: 800;
  color: #fff;
  margin: 0 0 16px;
}
.sg-cta-text > p {
  font-size: 1rem;
  color: rgba(255,255,255,0.75);
  line-height: 1.7;
  margin-bottom: 24px;
}
.sg-cta-features {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.sg-cta-features li {
  color: rgba(255,255,255,0.8);
  font-size: 0.9rem;
  padding-left: 20px;
  position: relative;
}
.sg-cta-features li::before {
  content: '✓';
  position: absolute;
  left: 0;
  color: #4da8ff;
  font-weight: 700;
}
.sg-cta-actions {
  display: flex;
  flex-direction: column;
  gap: 14px;
  min-width: 220px;
}
.btn-outline-white {
  background: transparent;
  border: 2px solid rgba(255,255,255,0.5);
  color: #fff;
  padding: 14px 28px;
  border-radius: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  text-decoration: none;
  text-align: center;
  transition: all 0.2s;
  display: inline-block;
}
.btn-outline-white:hover {
  border-color: #fff;
  background: rgba(255,255,255,0.1);
}

/* ---- BACK TO TOP ---- */
.back-to-top {
  position: fixed;
  bottom: 32px;
  right: 32px;
  width: 44px;
  height: 44px;
  background: #1a4fa0;
  color: #fff;
  border: none;
  border-radius: 50%;
  font-size: 1.2rem;
  cursor: pointer;
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 0.3s, transform 0.3s;
  z-index: 200;
  box-shadow: 0 4px 16px rgba(0,0,0,0.3);
}
.back-to-top.visible {
  opacity: 1;
  transform: translateY(0);
}
.back-to-top:hover { background: #2563eb; }

/* ---- SHARED BUTTON OVERRIDES ---- */
.btn-lg {
  padding: 14px 32px;
  font-size: 1rem;
}
.btn-sm {
  padding: 8px 18px;
  font-size: 0.85rem;
}
.btn-primary {
  background: linear-gradient(135deg, #1a4fa0, #2563eb);
  color: #fff;
  border: none;
  border-radius: 8px;
  font-weight: 600;
  text-decoration: none;
  display: inline-block;
  text-align: center;
  transition: all 0.2s;
  cursor: pointer;
}
.btn-primary:hover { background: linear-gradient(135deg, #2563eb, #3b82f6); transform: translateY(-1px); }
.btn-outline {
  background: transparent;
  border: 2px solid rgba(255,255,255,0.45);
  color: #fff;
  border-radius: 8px;
  font-weight: 600;
  text-decoration: none;
  display: inline-block;
  text-align: center;
  transition: all 0.2s;
}
.btn-outline:hover { border-color: #fff; background: rgba(255,255,255,0.08); }

/* ---- SECTION TAG ---- */
.section-tag {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: #4da8ff;
  background: rgba(77,168,255,0.1);
  border: 1px solid rgba(77,168,255,0.25);
  padding: 4px 12px;
  border-radius: 20px;
  margin-bottom: 8px;
}

/* ---- RESPONSIVE ---- */
@media (max-width: 1024px) {
  .sg-two-col, .sg-two-col-narrow {
    grid-template-columns: 1fr;
  }
  .sg-two-col-reverse { direction: ltr; }
  .env-matrix {
    grid-template-columns: 1fr;
  }
  .standards-grid {
    grid-template-columns: 1fr;
  }
  .pitfalls-grid {
    grid-template-columns: 1fr;
  }
  .sg-cta-inner {
    grid-template-columns: 1fr;
  }
  .sg-cta-actions {
    flex-direction: row;
    flex-wrap: wrap;
  }
}
@media (max-width: 768px) {
  .sg-hero { min-height: 480px; padding-bottom: 48px; }
  .sg-chapter { padding: 64px 0; }
  .chapter-header { flex-direction: column; gap: 16px; }
  .chapter-num-badge { width: 48px; height: 48px; font-size: 1.1rem; }
  .sc-criterion { flex-direction: column; }
  .voltage-flow { flex-direction: column; }
  .vf-arrow { transform: rotate(90deg); }
  .sg-hero-cta { flex-direction: column; }
  .sg-hero-cta .btn { width: 100%; text-align: center; }
}
@media (max-width: 480px) {
  .chapter-nav-inner { gap: 0; }
  .ch-link { padding: 14px 12px; font-size: 0.75rem; }
  .ch-num { display: none; }
}