* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --bg-dark: #0f1117;
  --bg-card: #1a1d27;
  --bg-card-hover: #222636;
  --accent: #7c6ef5;
  --accent-glow: rgba(124, 110, 245, 0.25);
  --text-primary: #f0f0f5;
  --text-secondary: #8889a0;
  --text-muted: #565870;
  --border: #2c2f3e;
  --tag-bg: #24273a;
  --tag-text: #9a9bb8;
}

body {
  font-family: 'Inter', sans-serif;
  background: var(--bg-dark);
  color: var(--text-primary);
  min-height: 100vh;
  line-height: 1.6;
}

/* ─── Header ─── */
header {
  text-align: center;
  padding: 80px 20px 60px;
  position: relative;
}

header::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 80px;
  height: 3px;
  background: var(--accent);
  border-radius: 2px;
}

header h1 {
  font-family: 'Playfair Display', serif;
  font-size: clamp(2.4rem, 5vw, 3.8rem);
  font-weight: 900;
  letter-spacing: -0.02em;
  margin-bottom: 14px;
  background: linear-gradient(135deg, #fff 40%, var(--accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

header p {
  color: var(--text-secondary);
  font-size: 1.05rem;
  font-weight: 300;
  max-width: 560px;
  margin: 0 auto;
}

/* ─── Nav Tabs ─── */
.nav-tabs {
  display: flex;
  justify-content: center;
  gap: 8px;
  padding: 30px 20px 0;
  flex-wrap: wrap;
}

.nav-tab {
  padding: 9px 22px;
  border: 1px solid var(--border);
  border-radius: 30px;
  background: transparent;
  color: var(--text-secondary);
  font-family: 'Inter', sans-serif;
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.25s ease;
}

.nav-tab:hover {
  border-color: var(--accent);
  color: var(--text-primary);
}

.nav-tab.active {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
  box-shadow: 0 4px 14px var(--accent-glow);
}

/* ─── Section Wrapper ─── */
.section {
  display: none;
  max-width: 1100px;
  margin: 0 auto;
  padding: 50px 20px 80px;
  animation: fadeIn 0.35s ease;
}

.section.active { display: block; }

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(12px); }
  to   { opacity: 1; transform: translateY(0); }
}

.section-title {
  font-family: 'Inter', sans-serif;
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--accent);
  margin-bottom: 28px;
}

/* ─── Font Pair Cards ─── */
.pair-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 22px;
}

.pair-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 32px;
  transition: border-color 0.3s, box-shadow 0.3s;
}

.pair-card:hover {
  border-color: var(--accent);
  box-shadow: 0 0 22px var(--accent-glow);
}

.pair-card .label {
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--text-muted);
  margin-bottom: 18px;
}

.pair-card .heading-demo {
  font-size: 1.7rem;
  font-weight: 700;
  line-height: 1.25;
  color: var(--text-primary);
  margin-bottom: 10px;
}

.pair-card .body-demo {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 20px;
}

.pair-card .tags {
  display: flex;
  flex-wrap: wrap;
  gap: 7px;
}

.tag {
  font-size: 0.7rem;
  font-weight: 500;
  background: var(--tag-bg);
  color: var(--tag-text);
  padding: 4px 11px;
  border-radius: 20px;
}

/* ─── Hierarchy Demo ─── */
.hierarchy-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 48px 40px;
  margin-bottom: 22px;
  transition: border-color 0.3s;
}

.hierarchy-card:hover {
  border-color: var(--accent);
}

.hierarchy-card .meta {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 32px;
}

.hierarchy-card .meta-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--accent);
}

.hierarchy-card .meta-text {
  font-size: 0.72rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--text-muted);
}

.h-row {
  display: flex;
  align-items: baseline;
  gap: 22px;
  padding: 14px 0;
  border-bottom: 1px solid var(--border);
}

.h-row:last-child { border-bottom: none; }

.h-tag {
  font-family: 'Roboto Mono', monospace;
  font-size: 0.7rem;
  color: var(--accent);
  min-width: 38px;
  font-weight: 500;
}

.h-size {
  font-size: 0.68rem;
  color: var(--text-muted);
  min-width: 72px;
  font-family: 'Roboto Mono', monospace;
}

.h-text { color: var(--text-primary); }

/* ─── Scale Demo ─── */
.scale-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 40px;
  margin-bottom: 22px;
}

.scale-row {
  display: flex;
  align-items: baseline;
  gap: 18px;
  padding: 10px 0;
  border-bottom: 1px solid var(--border);
}

.scale-row:last-child { border-bottom: none; }

.scale-label {
  font-family: 'Roboto Mono', monospace;
  font-size: 0.68rem;
  color: var(--accent);
  min-width: 100px;
}

.scale-value {
  font-family: 'Roboto Mono', monospace;
  font-size: 0.68rem;
  color: var(--text-muted);
  min-width: 52px;
}

.scale-text { color: var(--text-primary); }

/* ─── Readability Section ─── */
.read-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 22px;
}

.read-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 14px;
  overflow: hidden;
  transition: border-color 0.3s;
}

.read-card:hover { border-color: var(--accent); }

.read-card-header {
  padding: 18px 24px;
  border-bottom: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.read-card-header span {
  font-size: 0.72rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
}

.score {
  font-family: 'Roboto Mono', monospace;
  font-size: 0.72rem;
  color: var(--accent);
  background: var(--tag-bg);
  padding: 3px 9px;
  border-radius: 12px;
}

.read-card-body {
  padding: 24px;
}

.read-card-body p {
  color: var(--text-secondary);
  line-height: 1.85;
  font-size: 0.88rem;
}

.read-card-body .font-info {
  margin-top: 16px;
  padding-top: 14px;
  border-top: 1px solid var(--border);
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}

.read-card-body .info-item {
  font-size: 0.68rem;
  color: var(--text-muted);
}

.read-card-body .info-item strong {
  color: var(--tag-text);
}

/* ─── Specimen ─── */
.specimen-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 48px 40px;
  margin-bottom: 22px;
  text-align: center;
}

.specimen-card .sp-name {
  font-size: 0.72rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--accent);
  margin-bottom: 30px;
}

.specimen-card .sp-alpha {
  font-size: clamp(1.5rem, 3vw, 2.2rem);
  color: var(--text-primary);
  letter-spacing: 0.04em;
  line-height: 1.6;
  margin-bottom: 18px;
}

.specimen-card .sp-numbers {
  font-size: 1.4rem;
  color: var(--text-secondary);
  letter-spacing: 0.06em;
  margin-bottom: 18px;
}

.specimen-card .sp-symbols {
  font-size: 1.1rem;
  color: var(--text-muted);
  letter-spacing: 0.08em;
  margin-bottom: 28px;
}

.specimen-card .sp-weights {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 24px;
}

.sp-weight-item {
  text-align: center;
}

.sp-weight-item .w-label {
  font-size: 0.65rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: 6px;
}

.sp-weight-item .w-sample {
  font-size: 1.15rem;
  color: var(--text-secondary);
}

/* ─── Responsive ─── */
@media (max-width: 640px) {
  .pair-grid, .read-grid {
    grid-template-columns: 1fr;
  }

  .hierarchy-card, .scale-card {
    padding: 28px 22px;
  }

  .h-row {
    flex-wrap: wrap;
    gap: 6px;
  }

  .specimen-card {
    padding: 34px 22px;
  }
}