/* ============================================
   MOOCAI 官网 - 全局样式
   色调：科技蓝 #008F7A + 简约白
   ============================================ */

:root {
  --primary: #008F7A;
  --primary-dark: #00695C;
  --primary-light: #E0F2F1;
  --primary-soft: #B2DFDB;
  --accent: #26A69A;
  --text: #1E293B;
  --text-secondary: #64748B;
  --text-light: #94A3B8;
  --bg: #FFFFFF;
  --bg-soft: #F8FAFC;
  --bg-card: #FFFFFF;
  --border: #E2E8F0;
  --border-light: #F1F5F9;
  --shadow: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.08);
  --shadow-lg: 0 10px 40px rgba(37,99,235,0.12);
  --radius: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --max-width: 1200px;
  --nav-height: 64px;
  --transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--primary); text-decoration: none; transition: var(--transition); }
a:hover { color: var(--primary-dark); }

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

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

/* ============================================
   导航栏
   ============================================ */
.navbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--nav-height);
  background: rgba(255,255,255,0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-light);
  z-index: 1000;
  transition: var(--transition);
}

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

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 20px;
  font-weight: 700;
  color: var(--text);
}

.logo-icon {
  width: 36px; height: 36px;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  flex-shrink: 0;
}
.logo-icon img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 32px;
  list-style: none;
}

.nav-links a {
  color: var(--text-secondary);
  font-size: 15px;
  font-weight: 500;
  position: relative;
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--primary);
}

.nav-links a.active::after {
  content: '';
  position: absolute;
  bottom: -6px;
  left: 0; right: 0;
  height: 2px;
  background: var(--primary);
  border-radius: 2px;
}

.nav-cta {
  padding: 8px 20px;
  background: var(--primary);
  color: #fff !important;
  border-radius: 8px;
  font-size: 14px;
  font-weight: 600;
}

.nav-cta:hover {
  background: var(--primary-dark);
  color: #fff !important;
  transform: translateY(-1px);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  padding: 8px;
}

.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--text);
  border-radius: 2px;
  transition: var(--transition);
}

/* ============================================
   按钮
   ============================================ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 28px;
  border-radius: 10px;
  font-size: 15px;
  font-weight: 600;
  border: none;
  cursor: pointer;
  transition: var(--transition);
}

.btn-primary {
  background: linear-gradient(135deg, var(--primary), var(--accent));
  color: #fff;
  box-shadow: 0 4px 14px rgba(37,99,235,0.35);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(37,99,235,0.45);
  color: #fff;
}

.btn-secondary {
  background: var(--bg-soft);
  color: var(--text);
  border: 1px solid var(--border);
}

.btn-secondary:hover {
  background: var(--border-light);
  border-color: var(--primary-soft);
}

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

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

.btn-lg { padding: 14px 36px; font-size: 16px; border-radius: 12px; }

.btn-sm { padding: 8px 18px; font-size: 13px; border-radius: 8px; }

/* ============================================
   Hero 区域
   ============================================ */
.hero {
  padding: calc(var(--nav-height) + 80px) 0 100px;
  background: linear-gradient(180deg, var(--primary-light) 0%, var(--bg) 60%);
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -50%; right: -20%;
  width: 600px; height: 600px;
  background: radial-gradient(circle, rgba(37,99,235,0.08) 0%, transparent 70%);
  pointer-events: none;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 60px;
  align-items: center;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 16px;
  background: rgba(37,99,235,0.08);
  color: var(--primary);
  border-radius: 100px;
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 20px;
}

.hero h1 {
  font-size: 48px;
  font-weight: 800;
  line-height: 1.15;
  margin-bottom: 20px;
  letter-spacing: -0.02em;
}

.hero h1 span {
  background: linear-gradient(135deg, var(--primary), var(--accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  font-size: 18px;
  color: var(--text-secondary);
  margin-bottom: 36px;
  max-width: 480px;
}

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

.hero-stats {
  display: flex;
  gap: 40px;
  margin-top: 48px;
  padding-top: 32px;
  border-top: 1px solid var(--border-light);
}

.hero-stat strong {
  display: block;
  font-size: 28px;
  font-weight: 800;
  color: var(--primary);
}

.hero-stat span {
  font-size: 14px;
  color: var(--text-light);
}

.hero-visual {
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
}

.hero-mockup {
  width: 100%;
  max-width: 520px;
  background: var(--bg-card);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-lg);
  border: 1px solid var(--border-light);
  padding: 24px;
  position: relative;
}

.mockup-header {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border-light);
}

.mockup-dot { width: 10px; height: 10px; border-radius: 50%; }

.mockup-chat {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.chat-bubble {
  padding: 12px 16px;
  border-radius: 16px;
  font-size: 14px;
  max-width: 85%;
}

.chat-bubble.user {
  align-self: flex-end;
  background: var(--primary);
  color: #fff;
  border-bottom-right-radius: 4px;
}

.chat-bubble.ai {
  align-self: flex-start;
  background: var(--bg-soft);
  color: var(--text);
  border-bottom-left-radius: 4px;
}

/* ============================================
   板块标题
   ============================================ */
.section-header {
  text-align: center;
  margin-bottom: 60px;
}

.section-header h2 {
  font-size: 36px;
  font-weight: 800;
  margin-bottom: 12px;
}

.section-header p {
  font-size: 17px;
  color: var(--text-secondary);
  max-width: 560px;
  margin: 0 auto;
}

.section-tag {
  display: inline-block;
  padding: 4px 14px;
  background: var(--primary-light);
  color: var(--primary);
  border-radius: 100px;
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 16px;
}

/* ============================================
   功能卡片
   ============================================ */
.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 24px;
}

.feature-card {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-lg);
  padding: 32px;
  transition: var(--transition);
}

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

.feature-icon {
  width: 52px; height: 52px;
  border-radius: 14px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 24px;
  margin-bottom: 20px;
  background: var(--primary-light);
}

.feature-card h3 {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 10px;
}

.feature-card p {
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* ============================================
   下载卡片
   ============================================ */
.download-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 24px;
}

.download-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 36px;
  text-align: center;
  transition: var(--transition);
}

.download-card:hover {
  border-color: var(--primary-soft);
  box-shadow: var(--shadow-md);
}

.download-card .browser-icon {
  width: 64px; height: 64px;
  margin: 0 auto 20px;
  font-size: 48px;
}

.download-card h3 {
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 8px;
}

.download-card p {
  font-size: 14px;
  color: var(--text-secondary);
  margin-bottom: 24px;
}

/* ============================================
   定价卡片
   ============================================ */
.pricing-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
  max-width: 960px;
  margin: 0 auto;
}

.pricing-card {
  background: var(--bg-card);
  border: 2px solid var(--border-light);
  border-radius: var(--radius-lg);
  padding: 36px 28px;
  text-align: center;
  transition: var(--transition);
  position: relative;
}

.pricing-card:hover {
  border-color: var(--primary-soft);
}

.pricing-card.popular {
  border-color: var(--primary);
  box-shadow: var(--shadow-lg);
  transform: scale(1.03);
}

.popular-badge {
  position: absolute;
  top: -12px;
  left: 50%;
  transform: translateX(-50%);
  padding: 4px 16px;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  color: #fff;
  border-radius: 100px;
  font-size: 12px;
  font-weight: 700;
}

.pricing-card h3 {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 4px;
}

.pricing-card .price {
  font-size: 42px;
  font-weight: 800;
  color: var(--primary);
  margin: 16px 0 4px;
}

.pricing-card .price span {
  font-size: 16px;
  font-weight: 500;
  color: var(--text-light);
}

.pricing-card .period {
  font-size: 14px;
  color: var(--text-light);
  margin-bottom: 24px;
}

.pricing-features {
  list-style: none;
  text-align: left;
  margin-bottom: 28px;
}

.pricing-features li {
  padding: 8px 0;
  font-size: 14px;
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  gap: 10px;
}

.pricing-features li::before {
  content: '';
  display: inline-block;
  width: 18px; height: 18px;
  background: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%232563EB' stroke-width='2.5' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='20 6 9 17 4 12'/%3E%3C/svg%3E") center/contain no-repeat;
  flex-shrink: 0;
}

/* ============================================
   FAQ 手风琴
   ============================================ */
.faq-list {
  max-width: 720px;
  margin: 0 auto;
}

.faq-item {
  border: 1px solid var(--border-light);
  border-radius: var(--radius);
  margin-bottom: 12px;
  overflow: hidden;
  background: var(--bg-card);
}

.faq-question {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 18px 24px;
  cursor: pointer;
  font-weight: 600;
  font-size: 15px;
  transition: var(--transition);
}

.faq-question:hover {
  background: var(--bg-soft);
}

.faq-question::after {
  content: '+';
  font-size: 22px;
  color: var(--primary);
  font-weight: 400;
  transition: var(--transition);
}

.faq-item.active .faq-question::after {
  transform: rotate(45deg);
}

.faq-answer {
  padding: 0 24px;
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease, padding 0.3s ease;
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.8;
}

.faq-item.active .faq-answer {
  padding: 0 24px 20px;
  max-height: 500px;
}

/* ============================================
   步骤
   ============================================ */
.steps {
  display: flex;
  justify-content: center;
  gap: 40px;
  flex-wrap: wrap;
}

.step {
  text-align: center;
  max-width: 200px;
}

.step-num {
  width: 48px; height: 48px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  font-weight: 700;
  margin: 0 auto 16px;
}

.step h4 {
  font-size: 16px;
  font-weight: 700;
  margin-bottom: 6px;
}

.step p {
  font-size: 14px;
  color: var(--text-secondary);
}

/* ============================================
   页脚
   ============================================ */
.footer {
  background: var(--bg-soft);
  border-top: 1px solid var(--border-light);
  padding: 60px 0 30px;
}

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

.footer-brand p {
  font-size: 14px;
  color: var(--text-secondary);
  margin-top: 12px;
  line-height: 1.8;
}

.footer-links h4 {
  font-size: 14px;
  font-weight: 700;
  margin-bottom: 16px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.footer-links ul {
  list-style: none;
}

.footer-links li {
  margin-bottom: 10px;
}

.footer-links a {
  color: var(--text-secondary);
  font-size: 14px;
}

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

.footer-bottom {
  padding-top: 24px;
  border-top: 1px solid var(--border-light);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px;
}

.footer-bottom p {
  font-size: 13px;
  color: var(--text-light);
}

/* ============================================
   内容页通用
   ============================================ */
.page-header {
  padding: calc(var(--nav-height) + 60px) 0 60px;
  background: linear-gradient(180deg, var(--primary-light) 0%, var(--bg) 70%);
  text-align: center;
}

.page-header h1 {
  font-size: 40px;
  font-weight: 800;
  margin-bottom: 12px;
}

.page-header p {
  font-size: 17px;
  color: var(--text-secondary);
  max-width: 560px;
  margin: 0 auto;
}

.page-section {
  padding: 80px 0;
}

.page-section:nth-child(even) {
  background: var(--bg-soft);
}

/* 文本内容页 */
.content-page {
  max-width: 800px;
  margin: 0 auto;
  padding: 40px 24px;
}

.content-page h2 {
  font-size: 24px;
  font-weight: 700;
  margin: 40px 0 16px;
  padding-bottom: 10px;
  border-bottom: 2px solid var(--primary-light);
}

.content-page h3 {
  font-size: 18px;
  font-weight: 700;
  margin: 28px 0 12px;
}

.content-page p {
  margin-bottom: 16px;
  color: var(--text-secondary);
  line-height: 1.8;
}

.content-page ul {
  margin: 16px 0;
  padding-left: 24px;
  color: var(--text-secondary);
}

.content-page li {
  margin-bottom: 8px;
  line-height: 1.7;
}

.content-page .effective-date {
  color: var(--text-light);
  font-size: 14px;
  margin-bottom: 32px;
}

/* ============================================
   更新日志
   ============================================ */
.changelog-item {
  display: flex;
  gap: 24px;
  padding: 24px 0;
  border-bottom: 1px solid var(--border-light);
}

.changelog-version {
  min-width: 100px;
  font-weight: 700;
  color: var(--primary);
  font-size: 16px;
}

.changelog-date {
  font-size: 13px;
  color: var(--text-light);
  margin-top: 4px;
}

.changelog-content h4 {
  font-size: 16px;
  margin-bottom: 8px;
}

.changelog-content ul {
  list-style: none;
  padding: 0;
}

.changelog-content li {
  padding: 4px 0;
  font-size: 14px;
  color: var(--text-secondary);
}

.changelog-content li::before {
  content: '· ';
  color: var(--primary);
  font-weight: 700;
}

/* ============================================
   响应式
   ============================================ */
@media (max-width: 992px) {
  .hero-grid { grid-template-columns: 1fr; text-align: center; }
  .hero p { margin: 0 auto 36px; }
  .hero-btns { justify-content: center; }
  .hero-stats { justify-content: center; }
  .hero-visual { order: -1; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 768px) {
  .nav-links { display: none; position: absolute; top: var(--nav-height); left: 0; right: 0; background: var(--bg); flex-direction: column; padding: 16px 24px; border-bottom: 1px solid var(--border); box-shadow: var(--shadow-md); }
  .nav-links.open { display: flex; }
  .nav-toggle { display: flex; }
  .hero h1 { font-size: 32px; }
  .hero p { font-size: 16px; }
  .section-header h2 { font-size: 28px; }
  .pricing-card.popular { transform: none; }
  .footer-grid { grid-template-columns: 1fr; gap: 32px; }
  .footer-bottom { flex-direction: column; text-align: center; }
  .steps { flex-direction: column; align-items: center; }
}

@media (max-width: 480px) {
  .hero { padding-top: calc(var(--nav-height) + 60px); padding-bottom: 60px; }
  .hero h1 { font-size: 28px; }
  .hero-stats { gap: 24px; }
  .hero-stat strong { font-size: 22px; }
  .page-header h1 { font-size: 28px; }
  .page-section { padding: 60px 0; }
}