:root {
  --bg: #eef3f8;
  --panel: #ffffff;
  --panel-soft: #f7fafc;
  --text: #132339;
  --muted: #5f7287;
  --line: #d8e2ec;
  --brand: #0d6efd;
  --brand-dark: #0a56bf;
  --accent: #0f9d7a;
  --shadow: 0 18px 50px rgba(10, 35, 66, 0.08);
  --radius-xl: 26px;
  --radius-lg: 18px;
  --radius-md: 14px;
  --font-head: "Georgia", "Times New Roman", serif;
  --font-body: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  min-height: 100%;
  background:
    radial-gradient(circle at top left, rgba(13, 110, 253, 0.12), transparent 32%),
    radial-gradient(circle at bottom right, rgba(15, 157, 122, 0.11), transparent 28%),
    var(--bg);
  color: var(--text);
  font-family: var(--font-body);
}

body {
  line-height: 1.6;
}

a {
  color: var(--brand);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

img {
  max-width: 100%;
  display: block;
}

.shell {
  width: min(1180px, calc(100% - 32px));
  margin: 0 auto;
}

.topbar {
  padding: 18px 0;
}

.topbar-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}

.brand {
  display: flex;
  align-items: center;
  gap: 14px;
}

.brand-mark {
  width: 44px;
  height: 44px;
  border-radius: 14px;
  background: linear-gradient(135deg, var(--brand), var(--accent));
  box-shadow: var(--shadow);
}

.brand-copy strong,
.brand-copy span {
  display: block;
}

.brand-copy strong {
  font-size: 15px;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.brand-copy span {
  color: var(--muted);
  font-size: 13px;
}

.nav {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}

.nav a {
  color: var(--text);
  font-weight: 600;
}

.hero {
  padding: 20px 0 10px;
}

.hero-card,
.panel,
.product-card,
.detail-card,
.footer-card {
  background: rgba(255, 255, 255, 0.92);
  border: 1px solid var(--line);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow);
}

.hero-card {
  padding: 34px;
  display: grid;
  grid-template-columns: minmax(0, 1.45fr) minmax(320px, 0.95fr);
  gap: 28px;
}

.eyebrow {
  color: var(--brand);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  font-size: 12px;
  margin: 0 0 12px;
}

h1,
h2,
h3 {
  font-family: var(--font-head);
  line-height: 1.1;
  margin: 0;
}

h1 {
  font-size: clamp(38px, 6vw, 62px);
}

h2 {
  font-size: clamp(28px, 4vw, 42px);
}

h3 {
  font-size: 24px;
}

.lead {
  font-size: 18px;
  color: var(--muted);
  margin: 18px 0 0;
  max-width: 58ch;
}

.hero-actions,
.button-row,
.detail-actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.hero-actions {
  margin-top: 24px;
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 46px;
  padding: 0 18px;
  border-radius: 999px;
  border: 1px solid transparent;
  font-weight: 700;
  text-decoration: none;
  transition: transform 140ms ease, box-shadow 140ms ease, background 140ms ease;
}

.button:hover {
  text-decoration: none;
  transform: translateY(-1px);
}

.button.primary {
  background: linear-gradient(135deg, var(--brand), var(--brand-dark));
  color: #fff;
}

.button.secondary {
  border-color: var(--line);
  background: var(--panel);
  color: var(--text);
}

.hero-side {
  display: grid;
  gap: 16px;
  align-content: start;
}

.stat-grid {
  display: grid;
  gap: 14px;
}

.stat {
  background: var(--panel-soft);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 18px;
}

.stat strong,
.stat span {
  display: block;
}

.stat strong {
  font-size: 22px;
}

.stat span {
  color: var(--muted);
  margin-top: 6px;
}

.section {
  padding: 28px 0 0;
}

.section-header {
  display: grid;
  gap: 10px;
  margin-bottom: 18px;
}

.section-header p,
.callout p,
.detail-intro,
.muted {
  color: var(--muted);
}

.product-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 18px;
}

.product-card {
  padding: 22px;
  display: grid;
  gap: 14px;
}

.product-card.featured {
  background: linear-gradient(180deg, rgba(13, 110, 253, 0.12), rgba(255, 255, 255, 0.96));
  border-color: rgba(13, 110, 253, 0.35);
  box-shadow: 0 22px 60px rgba(13, 110, 253, 0.14);
}

.product-head {
  display: grid;
  grid-template-columns: 64px minmax(0, 1fr);
  gap: 14px;
  align-items: center;
}

.product-icon {
  width: 64px;
  height: 64px;
  border-radius: 18px;
  object-fit: cover;
  border: 1px solid var(--line);
  box-shadow: 0 10px 24px rgba(10, 35, 66, 0.12);
  background: #fff;
}

.product-title {
  display: grid;
  gap: 6px;
}

.product-card p {
  margin: 0;
}

.tag {
  display: inline-flex;
  align-items: center;
  width: fit-content;
  border-radius: 999px;
  background: rgba(13, 110, 253, 0.1);
  color: var(--brand);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  padding: 6px 10px;
}

.note {
  padding: 18px 20px;
  border-left: 4px solid var(--accent);
  background: rgba(15, 157, 122, 0.08);
  border-radius: var(--radius-md);
}

.textbook {
  display: grid;
  grid-template-columns: minmax(0, 1.2fr) minmax(260px, 0.8fr);
  gap: 22px;
  padding: 26px;
}

.bullet-list {
  padding-left: 18px;
  margin: 12px 0 0;
}

.bullet-list li + li {
  margin-top: 8px;
}

.callout {
  padding: 22px;
  background: linear-gradient(180deg, rgba(13, 110, 253, 0.08), rgba(255, 255, 255, 0.94));
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
}

.footer {
  padding: 30px 0 40px;
}

.footer-card {
  padding: 24px;
  display: grid;
  gap: 14px;
}

.footer-links {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}

.detail-layout {
  padding: 18px 0 40px;
}

.detail-card {
  padding: 30px;
  display: grid;
  gap: 20px;
}

.detail-meta {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.pill {
  display: inline-flex;
  align-items: center;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--panel-soft);
  color: var(--muted);
  font-size: 13px;
  font-weight: 600;
  padding: 7px 12px;
}

.detail-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.25fr) minmax(260px, 0.75fr);
  gap: 22px;
}

.detail-sidebar {
  display: grid;
  gap: 16px;
  align-content: start;
}

.detail-panel {
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background: var(--panel-soft);
  padding: 18px;
}

.detail-panel h3 {
  font-size: 19px;
}

.detail-panel p,
.detail-panel ul {
  margin: 12px 0 0;
}

.detail-panel ul {
  padding-left: 18px;
}

.home-link {
  font-weight: 700;
}

@media (max-width: 980px) {
  .hero-card,
  .textbook,
  .detail-grid {
    grid-template-columns: 1fr;
  }

  .product-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 720px) {
  .shell {
    width: min(100% - 20px, 1180px);
  }

  .hero-card,
  .detail-card,
  .footer-card,
  .textbook {
    padding: 22px;
  }

  .product-grid {
    grid-template-columns: 1fr;
  }
}