/* ============================================================
   比特币投资指南 - 主样式表
   版本: 2.0 | 最后更新: 2026-06-21
   ============================================================ */

/* --- 全局重置 --- */
*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

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

body {
  font-family: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', sans-serif;
  line-height: 1.7;
  color: #1f2937;
  background-color: #ffffff;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* --- 通用样式 --- */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}

a {
  color: #1e40af;
  text-decoration: none;
  transition: color 0.25s ease;
}

a:hover {
  color: #1e3a8a;
  text-decoration: underline;
}

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  border-radius: 6px;
  transition: all 0.25s ease;
  outline: none;
}

button:focus-visible {
  outline: 2px solid #f97316;
  outline-offset: 2px;
}

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

/* --- 头部导航 --- */
header {
  background-color: #ffffff;
  border-bottom: 1px solid #e5e7eb;
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
  backdrop-filter: blur(8px);
}

nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 18px 0;
}

.logo {
  font-size: 22px;
  font-weight: 700;
  color: #1e40af;
  letter-spacing: -0.5px;
}

.nav-links {
  display: flex;
  gap: 28px;
  list-style: none;
}

.nav-links a {
  font-size: 14px;
  font-weight: 500;
  color: #4b5563;
  position: relative;
  padding: 4px 0;
}

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background: #1e40af;
  transition: width 0.25s ease;
}

.nav-links a:hover {
  color: #1e40af;
  text-decoration: none;
}

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

/* --- Hero区域 --- */
.hero {
  background: linear-gradient(135deg, #1e40af 0%, #1e3a8a 50%, #172554 100%);
  color: #ffffff;
  padding: 100px 0 90px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(circle at 30% 50%, rgba(249, 115, 22, 0.08) 0%, transparent 50%);
  animation: heroGlow 8s ease-in-out infinite alternate;
}

@keyframes heroGlow {
  from { transform: translate(0, 0); }
  to { transform: translate(20px, -10px); }
}

.hero .container {
  position: relative;
  z-index: 1;
}

.hero h1 {
  font-size: 44px;
  font-weight: 700;
  margin-bottom: 24px;
  line-height: 1.25;
  letter-spacing: -1px;
}

.hero p {
  font-size: 18px;
  margin-bottom: 36px;
  opacity: 0.92;
  max-width: 680px;
  margin-left: auto;
  margin-right: auto;
  line-height: 1.8;
}

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

.btn {
  padding: 14px 36px;
  font-size: 16px;
  font-weight: 600;
  border-radius: 8px;
  transition: all 0.3s ease;
  display: inline-block;
}

.btn-primary {
  background-color: #f97316;
  color: #ffffff;
  box-shadow: 0 2px 8px rgba(249, 115, 22, 0.3);
}

.btn-primary:hover {
  background-color: #ea580c;
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(249, 115, 22, 0.4);
}

.btn-secondary {
  background-color: rgba(255, 255, 255, 0.12);
  color: #ffffff;
  border: 2px solid rgba(255, 255, 255, 0.6);
}

.btn-secondary:hover {
  background-color: rgba(255, 255, 255, 0.22);
  border-color: #ffffff;
  transform: translateY(-2px);
}

/* --- 快速导航 --- */
.quick-nav {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
}

.nav-card {
  background: #f8fafc;
  padding: 36px 28px;
  border-radius: 12px;
  text-align: center;
  transition: all 0.3s ease;
  border: 2px solid transparent;
  cursor: default;
}

.nav-card:hover {
  background: #ffffff;
  border-color: #1e40af;
  box-shadow: 0 8px 24px rgba(30, 64, 175, 0.1);
  transform: translateY(-5px);
}

.nav-card h3 {
  font-size: 19px;
  margin-bottom: 12px;
  color: #1e40af;
  font-weight: 600;
}

.nav-card p {
  font-size: 14px;
  color: #6b7280;
  line-height: 1.7;
}

/* --- 新手指南 / 教程区域 --- */
.guide-section {
  padding: 90px 0;
  background-color: #f9fafb;
}

.section-title {
  font-size: 34px;
  font-weight: 700;
  margin-bottom: 60px;
  text-align: center;
  color: #111827;
  letter-spacing: -0.5px;
}

.section-subtitle {
  font-size: 13px;
  color: #f97316;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 2px;
  margin-bottom: 12px;
  text-align: center;
}

.guide-steps {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 28px;
}

.step-card {
  background: #ffffff;
  padding: 32px 24px;
  border-radius: 12px;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.06);
  transition: all 0.3s ease;
  border: 1px solid #f1f5f9;
}

.step-card:hover {
  box-shadow: 0 10px 28px rgba(0, 0, 0, 0.1);
  transform: translateY(-5px);
  border-color: #bfdbfe;
}

.step-number {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  background: linear-gradient(135deg, #1e40af 0%, #3b82f6 100%);
  color: #ffffff;
  border-radius: 50%;
  font-size: 22px;
  font-weight: 700;
  margin-bottom: 18px;
  box-shadow: 0 4px 12px rgba(30, 64, 175, 0.25);
}

.step-card h3 {
  font-size: 17px;
  margin-bottom: 10px;
  color: #111827;
  font-weight: 600;
}

.step-card p {
  font-size: 14px;
  color: #6b7280;
  line-height: 1.75;
}

/* --- 交易所对比 --- */
.comparison-section {
  padding: 90px 0;
}

.table-wrapper {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.comparison-table {
  width: 100%;
  min-width: 720px;
  border-collapse: collapse;
  background: #ffffff;
  border-radius: 12px;
  overflow: hidden;
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.06);
}

.comparison-table thead {
  background-color: #1e40af;
  color: #ffffff;
}

.comparison-table th {
  padding: 18px 16px;
  text-align: left;
  font-weight: 600;
  font-size: 14px;
  letter-spacing: 0.3px;
}

.comparison-table td {
  padding: 16px;
  border-bottom: 1px solid #f1f5f9;
  font-size: 14px;
  color: #374151;
}

.comparison-table tbody tr:hover {
  background-color: #f8fafc;
}

.comparison-table tbody tr:last-child td {
  border-bottom: none;
}

.platform-name {
  font-weight: 600;
  color: #111827;
}

.badge {
  display: inline-block;
  padding: 4px 12px;
  border-radius: 20px;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.3px;
}

.badge-safe {
  background-color: #dcfce7;
  color: #166534;
}

.badge-warning {
  background-color: #fef3c7;
  color: #92400e;
}

/* --- 安全提示 --- */
.security-section {
  padding: 90px 0;
  background-color: #f9fafb;
}

.security-tips {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 28px;
}

.tip-card {
  background: #ffffff;
  padding: 32px 28px;
  border-radius: 12px;
  border-left: 4px solid #f97316;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.06);
  transition: all 0.3s ease;
}

.tip-card:hover {
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.1);
  transform: translateX(3px);
}

.tip-card h3 {
  font-size: 17px;
  margin-bottom: 10px;
  color: #111827;
  font-weight: 600;
}

.tip-card p {
  font-size: 14px;
  color: #6b7280;
  line-height: 1.75;
}

.tip-icon {
  font-size: 28px;
  margin-bottom: 12px;
}

/* --- 常见问题 --- */
.faq-section {
  padding: 90px 0;
}

.faq-container {
  max-width: 800px;
  margin: 0 auto;
}

.faq-item {
  margin-bottom: 16px;
  border: 1px solid #e5e7eb;
  border-radius: 10px;
  overflow: hidden;
  background: #ffffff;
  transition: box-shadow 0.3s ease;
}

.faq-item:hover {
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.06);
}

.faq-question {
  padding: 20px 24px;
  background-color: #f8fafc;
  cursor: pointer;
  font-weight: 600;
  font-size: 15px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: background-color 0.25s ease;
  user-select: none;
}

.faq-question:hover {
  background-color: #eff6ff;
}

.faq-toggle {
  font-size: 18px;
  transition: transform 0.3s ease;
  color: #1e40af;
  flex-shrink: 0;
  margin-left: 12px;
}

.faq-item.active .faq-toggle {
  transform: rotate(180deg);
}

.faq-answer {
  padding: 0 24px;
  max-height: 0;
  overflow: hidden;
  color: #4b5563;
  font-size: 14px;
  line-height: 1.8;
  transition: max-height 0.4s ease, padding 0.4s ease;
}

.faq-item.active .faq-answer {
  max-height: 600px;
  padding: 20px 24px;
}

/* --- 页脚 --- */
footer {
  background-color: #111827;
  color: #9ca3af;
  padding: 70px 0 24px;
}

.footer-content {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 40px;
  margin-bottom: 50px;
}

.footer-section h3 {
  color: #ffffff;
  margin-bottom: 18px;
  font-size: 15px;
  font-weight: 600;
}

.footer-section p {
  font-size: 14px;
  line-height: 1.8;
}

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

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

.footer-section a {
  color: #9ca3af;
  font-size: 14px;
  transition: color 0.25s ease;
}

.footer-section a:hover {
  color: #ffffff;
  text-decoration: none;
}

.footer-bottom {
  border-top: 1px solid #1f2937;
  padding-top: 24px;
  text-align: center;
  font-size: 13px;
  color: #6b7280;
  line-height: 1.8;
}

/* --- 响应式设计 --- */
@media (max-width: 768px) {
  .hero {
    padding: 70px 0 60px;
  }

  .hero h1 {
    font-size: 30px;
  }

  .hero p {
    font-size: 15px;
  }

  .nav-links {
    gap: 12px;
    flex-wrap: wrap;
    justify-content: flex-end;
  }

  .nav-links a {
    font-size: 12px;
  }

  .logo {
    font-size: 18px;
  }

  .section-title {
    font-size: 26px;
  }

  .comparison-table th,
  .comparison-table td {
    padding: 12px 10px;
    font-size: 12px;
  }

  .guide-steps,
  .security-tips {
    grid-template-columns: 1fr;
  }

  .btn {
    padding: 12px 24px;
    font-size: 14px;
  }

  .footer-content {
    grid-template-columns: 1fr 1fr;
    gap: 30px;
  }
}

@media (max-width: 480px) {
  .hero h1 {
    font-size: 24px;
  }

  .container {
    padding: 0 16px;
  }

  .footer-content {
    grid-template-columns: 1fr;
  }
}

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

.fade-in {
  opacity: 0;
  animation-fill-mode: forwards;
}