/* ============================================================
   德扑学院 / HHpoker — 学院知识风 Landing Page
   Design Token: sky-600 (#0284c7) + amber-400 (#fbbf24)
   Tone: 教学·成长·专业
   ============================================================ */

/* ----- CSS Variables ----- */
:root {
  --color-primary: #0284c7;
  --color-primary-light: #38bdf8;
  --color-primary-dark: #0369a1;
  --color-primary-bg: #f0f9ff;
  --color-accent: #fbbf24;
  --color-accent-dark: #f59e0b;
  --color-accent-light: #fef3c7;

  --color-white: #ffffff;
  --color-offwhite: #fafaf9;
  --color-gray-50: #f9fafb;
  --color-gray-100: #f3f4f6;
  --color-gray-200: #e5e7eb;
  --color-gray-300: #d1d5db;
  --color-gray-400: #9ca3af;
  --color-gray-500: #6b7280;
  --color-gray-600: #4b5563;
  --color-gray-700: #374151;
  --color-gray-800: #1f2937;
  --color-gray-900: #111827;

  --font-serif: 'Times New Roman', 'Georgia', 'STSong', 'SimSun', serif;
  --font-sans: 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', 'Helvetica Neue', Arial, sans-serif;

  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -4px rgba(0, 0, 0, 0.04);
  --shadow-card: 0 1px 3px rgba(0, 0, 0, 0.06), 0 1px 2px rgba(0, 0, 0, 0.04);

  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;

  --max-width: 1200px;
  --header-height: 72px;
}

/* ----- Reset & Base ----- */
*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.7;
  color: var(--color-gray-700);
  background-color: var(--color-white);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: color 0.25s ease;
}

a:hover {
  color: var(--color-primary-dark);
}

ul, ol {
  list-style: none;
}

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-serif);
  color: var(--color-gray-900);
  line-height: 1.3;
  font-weight: 700;
}

h1 { font-size: 2.75rem; letter-spacing: -0.02em; }
h2 { font-size: 2.25rem; letter-spacing: -0.01em; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }

p {
  margin-bottom: 1rem;
}

p:last-child {
  margin-bottom: 0;
}

/* ----- Utility ----- */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.section-label {
  display: inline-block;
  font-family: var(--font-sans);
  font-size: 0.875rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-primary);
  background: var(--color-primary-bg);
  padding: 4px 14px;
  border-radius: 9999px;
  margin-bottom: 12px;
}

.section-title {
  font-family: var(--font-serif);
  font-size: 2.25rem;
  font-weight: 700;
  color: var(--color-gray-900);
  margin-bottom: 16px;
}

.section-subtitle {
  font-size: 1.1rem;
  color: var(--color-gray-500);
  max-width: 640px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-family: var(--font-sans);
  font-size: 1rem;
  font-weight: 600;
  padding: 14px 32px;
  border-radius: var(--radius-md);
  border: none;
  cursor: pointer;
  transition: all 0.3s ease;
  text-align: center;
  white-space: nowrap;
}

.btn-primary {
  background: var(--color-primary);
  color: var(--color-white);
  box-shadow: 0 2px 8px rgba(2, 132, 199, 0.25);
}

.btn-primary:hover {
  background: var(--color-primary-dark);
  color: var(--color-white);
  box-shadow: 0 4px 16px rgba(2, 132, 199, 0.35);
  transform: translateY(-1px);
}

.btn-outline {
  background: transparent;
  color: var(--color-primary);
  border: 2px solid var(--color-primary);
}

.btn-outline:hover {
  background: var(--color-primary);
  color: var(--color-white);
}

.btn-accent {
  background: var(--color-accent);
  color: var(--color-gray-900);
  box-shadow: 0 2px 8px rgba(251, 191, 36, 0.3);
}

.btn-accent:hover {
  background: var(--color-accent-dark);
  color: var(--color-gray-900);
  box-shadow: 0 4px 16px rgba(251, 191, 36, 0.4);
  transform: translateY(-1px);
}

.btn-lg {
  font-size: 1.1rem;
  padding: 16px 40px;
  border-radius: var(--radius-lg);
}

/* ----- Header ----- */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-height);
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-gray-200);
  z-index: 1000;
  transition: box-shadow 0.3s ease;
}

.header.scrolled {
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.06);
}

.header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.header-logo {
  display: flex;
  align-items: baseline;
  gap: 10px;
}

.header-logo .logo-icon {
  width: 40px;
  height: 40px;
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-white);
  font-family: var(--font-serif);
  font-size: 1.25rem;
  font-weight: 700;
}

.header-logo .logo-text {
  display: flex;
  flex-direction: column;
}

.header-logo .logo-cn {
  font-family: var(--font-serif);
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-gray-900);
  line-height: 1.2;
}

.header-logo .logo-en {
  font-size: 0.7rem;
  font-weight: 500;
  color: var(--color-primary);
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.header-nav {
  display: flex;
  align-items: center;
  gap: 32px;
}

.header-nav a {
  font-size: 0.925rem;
  font-weight: 500;
  color: var(--color-gray-600);
  position: relative;
  padding: 4px 0;
}

.header-nav a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--color-primary);
  transition: width 0.3s ease;
}

.header-nav a:hover {
  color: var(--color-primary);
}

.header-nav a:hover::after {
  width: 100%;
}

.header-nav .btn {
  padding: 10px 24px;
  font-size: 0.9rem;
}

/* Mobile menu toggle */
.menu-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
  z-index: 1001;
}

.menu-toggle span {
  display: block;
  width: 26px;
  height: 2.5px;
  background: var(--color-gray-700);
  border-radius: 2px;
  transition: all 0.3s ease;
}

/* ----- Hero ----- */
.hero {
  padding: calc(var(--header-height) + 80px) 0 100px;
  background:
    linear-gradient(180deg, #ffffff 0%, #f0f9ff 40%, #e0f2fe 100%);
  background-size: 100% 100%;
  position: relative;
  overflow: hidden;
}

/* Paper texture overlay */
.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background:
    repeating-linear-gradient(
      0deg,
      transparent,
      transparent 2px,
      rgba(2, 132, 199, 0.015) 2px,
      rgba(2, 132, 199, 0.015) 4px
    );
  pointer-events: none;
  z-index: 0;
}

/* Book spine decorative */
.hero::after {
  content: '';
  position: absolute;
  right: 0;
  top: 15%;
  bottom: 15%;
  width: 6px;
  background: linear-gradient(180deg, var(--color-primary-light), var(--color-primary), var(--color-primary-dark));
  border-radius: 3px 0 0 3px;
  opacity: 0.25;
  z-index: 0;
}

.hero .container {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 60px;
  align-items: center;
}

.hero-content {
  max-width: 580px;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--color-white);
  border: 1px solid var(--color-gray-200);
  border-radius: 9999px;
  padding: 6px 18px;
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--color-gray-600);
  margin-bottom: 24px;
  box-shadow: var(--shadow-sm);
}

.hero-badge .dot {
  width: 8px;
  height: 8px;
  background: var(--color-accent);
  border-radius: 50%;
  animation: pulse-dot 2s infinite;
}

@keyframes pulse-dot {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.5; transform: scale(1.5); }
}

.hero-title {
  font-family: var(--font-serif);
  font-size: 3rem;
  font-weight: 800;
  color: var(--color-gray-900);
  line-height: 1.2;
  margin-bottom: 8px;
  letter-spacing: -0.02em;
}

.hero-title .highlight {
  color: var(--color-primary);
}

.hero-undertitle {
  font-family: var(--font-serif);
  font-size: 1.35rem;
  font-weight: 400;
  color: var(--color-gray-500);
  font-style: italic;
  margin-bottom: 24px;
  border-left: 3px solid var(--color-accent);
  padding-left: 16px;
}

.hero-desc {
  font-size: 1.05rem;
  color: var(--color-gray-600);
  line-height: 1.8;
  margin-bottom: 36px;
}

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

/* Hero visual — book card */
.hero-visual {
  display: flex;
  justify-content: center;
  align-items: center;
}

.hero-card {
  background: var(--color-white);
  border: 1px solid var(--color-gray-200);
  border-radius: var(--radius-xl);
  padding: 48px 40px;
  box-shadow: var(--shadow-lg);
  position: relative;
  max-width: 420px;
  width: 100%;
}

.hero-card::before {
  content: '';
  position: absolute;
  left: 0;
  top: 32px;
  bottom: 32px;
  width: 4px;
  background: linear-gradient(180deg, var(--color-primary-light), var(--color-primary), var(--color-primary-dark));
  border-radius: 0 2px 2px 0;
}

.hero-card .stat-row {
  display: flex;
  gap: 32px;
  margin-bottom: 28px;
}

.hero-card .stat-item {
  flex: 1;
}

.hero-card .stat-number {
  font-family: var(--font-serif);
  font-size: 2rem;
  font-weight: 800;
  color: var(--color-primary);
  line-height: 1;
}

.hero-card .stat-label {
  font-size: 0.8rem;
  color: var(--color-gray-400);
  margin-top: 6px;
}

.hero-card .quote-line {
  font-family: var(--font-serif);
  font-size: 1.15rem;
  font-style: italic;
  color: var(--color-gray-600);
  line-height: 1.6;
  padding-top: 20px;
  border-top: 1px solid var(--color-gray-200);
}

/* ----- Features (Stepped Numbering) ----- */
.features {
  padding: 100px 0;
  background: var(--color-white);
  position: relative;
}

.features-header {
  text-align: center;
  margin-bottom: 64px;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 32px;
}

.feature-card {
  background: var(--color-white);
  border: 1px solid var(--color-gray-200);
  border-radius: var(--radius-lg);
  padding: 36px 28px 28px;
  box-shadow: var(--shadow-card);
  transition: all 0.35s ease;
  position: relative;
  overflow: hidden;
}

.feature-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--color-primary-light);
}

.feature-card::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--color-primary), var(--color-primary-light));
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.4s ease;
}

.feature-card:hover::after {
  transform: scaleX(1);
}

.feature-number {
  font-family: var(--font-serif);
  font-size: 3.5rem;
  font-weight: 800;
  color: var(--color-gray-100);
  line-height: 1;
  margin-bottom: -8px;
  transition: color 0.35s ease;
  user-select: none;
}

.feature-card:hover .feature-number {
  color: var(--color-primary-bg);
}

.feature-card h3 {
  font-size: 1.2rem;
  margin-bottom: 10px;
  color: var(--color-gray-900);
}

.feature-card p {
  font-size: 0.925rem;
  color: var(--color-gray-500);
  line-height: 1.7;
}

/* ----- Vertical Dividers ----- */
.divider-section {
  padding: 0;
}

.divider-wrap {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0;
  padding: 40px 0;
}

.divider-line {
  flex: 1;
  height: 1px;
  background: var(--color-gray-200);
}

.divider-diamond {
  width: 8px;
  height: 8px;
  background: var(--color-primary);
  transform: rotate(45deg);
  margin: 0 20px;
  flex-shrink: 0;
}

/* ----- About Section ----- */
.about {
  padding: 100px 0;
  background: var(--color-gray-50);
}

.about .container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 80px;
  align-items: center;
}

.about-content h2 {
  margin-bottom: 24px;
}

.about-content .lead {
  font-size: 1.15rem;
  color: var(--color-gray-600);
  line-height: 1.8;
  margin-bottom: 20px;
}

.about-content .accent-text {
  font-family: var(--font-serif);
  font-size: 1.1rem;
  font-style: italic;
  color: var(--color-primary);
  border-left: 3px solid var(--color-accent);
  padding-left: 16px;
  margin: 28px 0;
}

.about-visual {
  position: relative;
}

.about-card {
  background: var(--color-white);
  border: 1px solid var(--color-gray-200);
  border-radius: var(--radius-xl);
  padding: 40px 36px;
  box-shadow: var(--shadow-md);
}

.about-card .pillars {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.about-card .pillar-item {
  display: flex;
  align-items: flex-start;
  gap: 16px;
}

.about-card .pillar-num {
  font-family: var(--font-serif);
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--color-primary);
  line-height: 1;
  flex-shrink: 0;
  min-width: 28px;
}

.about-card .pillar-info h4 {
  font-family: var(--font-sans);
  font-size: 1rem;
  color: var(--color-gray-900);
  margin-bottom: 4px;
}

.about-card .pillar-info p {
  font-size: 0.875rem;
  color: var(--color-gray-500);
  line-height: 1.6;
}

/* ----- Stats Bar ----- */
.stats-bar {
  padding: 64px 0;
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
  color: var(--color-white);
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 32px;
  text-align: center;
}

.stats-grid .stat-item {
  padding: 0 24px;
  border-right: 1px solid rgba(255, 255, 255, 0.2);
}

.stats-grid .stat-item:last-child {
  border-right: none;
}

.stats-grid .stat-number {
  font-family: var(--font-serif);
  font-size: 2.75rem;
  font-weight: 800;
  line-height: 1;
  margin-bottom: 8px;
}

.stats-grid .stat-label {
  font-size: 0.925rem;
  opacity: 0.85;
}

/* ----- CTA Section ----- */
.cta {
  padding: 100px 0;
  background: linear-gradient(180deg, #ffffff 0%, #f0f9ff 50%, #e0f2fe 100%);
  position: relative;
}

.cta::before {
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse at 30% 50%, rgba(2, 132, 199, 0.04) 0%, transparent 70%),
    radial-gradient(ellipse at 70% 50%, rgba(251, 191, 36, 0.04) 0%, transparent 70%);
  pointer-events: none;
}

.cta-inner {
  position: relative;
  z-index: 1;
  background: linear-gradient(135deg, var(--color-white), var(--color-primary-bg));
  border: 1px solid var(--color-gray-200);
  border-radius: var(--radius-xl);
  padding: 72px 60px;
  text-align: center;
  box-shadow: var(--shadow-lg);
  max-width: 800px;
  margin: 0 auto;
}

.cta-inner h2 {
  margin-bottom: 12px;
}

.cta-inner .cta-subtitle {
  font-size: 1.1rem;
  color: var(--color-gray-500);
  margin-bottom: 36px;
}

.cta-actions {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
}

.cta-note {
  margin-top: 20px;
  font-size: 0.85rem;
  color: var(--color-gray-400);
}

/* ----- Footer ----- */
.footer {
  background: var(--color-gray-100);
  border-top: 1px solid var(--color-gray-200);
  padding: 56px 0 32px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 40px;
}

.footer-brand .logo-cn {
  font-family: var(--font-serif);
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-gray-900);
  margin-bottom: 4px;
}

.footer-brand .logo-en {
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--color-primary);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  margin-bottom: 16px;
}

.footer-brand .brand-desc {
  font-size: 0.9rem;
  color: var(--color-gray-500);
  line-height: 1.7;
}

.footer-col h4 {
  font-family: var(--font-sans);
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--color-gray-800);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 20px;
}

.footer-col ul {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.footer-col a {
  font-size: 0.9rem;
  color: var(--color-gray-500);
  transition: color 0.25s ease;
}

.footer-col a:hover {
  color: var(--color-primary);
}

/* Customer Service Info */
.footer-cs {
  padding: 20px 0;
  border-top: 1px solid var(--color-gray-200);
  display: flex;
  justify-content: center;
  gap: 48px;
  flex-wrap: wrap;
}

.footer-cs .cs-item {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 0.9rem;
  color: var(--color-gray-600);
}

.footer-cs .cs-icon {
  width: 36px;
  height: 36px;
  background: var(--color-white);
  border: 1px solid var(--color-gray-200);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  font-size: 1rem;
}

.footer-cs .cs-text strong {
  display: block;
  color: var(--color-gray-800);
  font-weight: 600;
}

.footer-cs .cs-text span {
  color: var(--color-gray-500);
  font-size: 0.85rem;
}

.footer-bottom {
  padding-top: 24px;
  border-top: 1px solid var(--color-gray-200);
  text-align: center;
  font-size: 0.85rem;
  color: var(--color-gray-400);
}

.footer-bottom a {
  color: var(--color-gray-500);
}

.footer-bottom a:hover {
  color: var(--color-primary);
}

/* ============================================================
   Responsive
   ============================================================ */
@media (max-width: 1024px) {
  .features-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .hero .container {
    grid-template-columns: 1fr;
    gap: 48px;
  }

  .hero-visual {
    order: -1;
  }

  .hero-title {
    font-size: 2.5rem;
  }

  .about .container {
    grid-template-columns: 1fr;
    gap: 48px;
  }

  .footer-grid {
    grid-template-columns: 1fr 1fr;
    gap: 32px;
  }
}

@media (max-width: 768px) {
  :root {
    --header-height: 64px;
  }

  .header-nav {
    position: fixed;
    top: 0;
    right: -100%;
    width: 280px;
    height: 100vh;
    background: var(--color-white);
    flex-direction: column;
    padding: 100px 32px 32px;
    gap: 24px;
    box-shadow: -4px 0 20px rgba(0, 0, 0, 0.1);
    transition: right 0.4s ease;
    z-index: 1000;
  }

  .header-nav.active {
    right: 0;
  }

  .menu-toggle {
    display: flex;
  }

  h1 { font-size: 2rem; }
  h2 { font-size: 1.75rem; }

  .hero {
    padding: calc(var(--header-height) + 48px) 0 64px;
  }

  .hero-title {
    font-size: 2rem;
  }

  .hero-undertitle {
    font-size: 1.1rem;
  }

  .features {
    padding: 64px 0;
  }

  .features-grid {
    grid-template-columns: 1fr;
    gap: 24px;
  }

  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 24px;
  }

  .stats-grid .stat-item {
    border-right: none;
    border-bottom: 1px solid rgba(255, 255, 255, 0.2);
    padding-bottom: 20px;
  }

  .stats-grid .stat-item:nth-child(3),
  .stats-grid .stat-item:nth-child(4) {
    border-bottom: none;
  }

  .cta-inner {
    padding: 48px 28px;
  }

  .footer-grid {
    grid-template-columns: 1fr;
    gap: 28px;
  }

  .footer-cs {
    flex-direction: column;
    align-items: center;
    gap: 20px;
  }

  .hero-card {
    padding: 32px 24px;
  }

  .hero-card .stat-row {
    gap: 20px;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 16px;
  }

  .hero-actions {
    flex-direction: column;
  }

  .hero-actions .btn {
    width: 100%;
  }

  .stats-grid .stat-number {
    font-size: 2rem;
  }

  .btn-lg {
    padding: 14px 28px;
    font-size: 1rem;
  }
}

/* ============================================================
   Animations
   ============================================================ */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(24px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.fade-in-up {
  animation: fadeInUp 0.7s ease forwards;
  opacity: 0;
}

.delay-1 { animation-delay: 0.1s; }
.delay-2 { animation-delay: 0.2s; }
.delay-3 { animation-delay: 0.3s; }
.delay-4 { animation-delay: 0.4s; }
.delay-5 { animation-delay: 0.5s; }