/* ==========================================================================
   飞鸟云官网 - 原生极简高响应式 CSS
   遵循 W3C 语义化标准与 WCAG 2.1 AA 级对比度规范 (>= 4.5:1)
   ========================================================================== */

:root {
  --color-bg-primary: #0a0e17;
  --color-bg-secondary: rgba(17, 24, 39, 0.65);
  --color-bg-card: rgba(26, 34, 52, 0.72);
  --color-bg-card-hover: rgba(34, 45, 68, 0.85);
  --color-bg-glass: rgba(26, 34, 52, 0.85);

  --color-primary: #3b82f6;
  --color-primary-hover: #2563eb;
  --color-primary-light: #60a5fa;
  --color-accent: #06b6d4;
  --color-accent-gradient: linear-gradient(135deg, #3b82f6 0%, #06b6d4 100%);
  --color-warning: #f59e0b;
  --color-success: #10b981;

  --color-text-main: #f9fafb;
  --color-text-muted: #9ca3af;
  --color-text-subtle: #6b7280;
  --color-border: #2e384d;
  --color-border-focus: #60a5fa;

  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif;
  --container-max-width: 1200px;
  --header-height: 72px;
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 18px;
  --shadow-card: 0 10px 25px -5px rgba(0, 0, 0, 0.5), 0 8px 10px -6px rgba(0, 0, 0, 0.5);
  --transition-normal: 0.25s ease-in-out;
}

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

html {
  font-family: var(--font-sans);
  color: var(--color-text-main);
  line-height: 1.6;
  scroll-behavior: smooth;
  background-color: #0a0e17;
}

/* 全站沉浸式全局背景：调低背景亮度，强化文字辨识度 */
body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow-x: hidden;
  position: relative;
  background-color: #080c14;
  background-image: 
    linear-gradient(180deg, rgba(8, 12, 20, 0.65) 0%, rgba(10, 14, 23, 0.78) 45%, rgba(10, 14, 23, 0.90) 100%),
    url('hero-bg.jpg');
  background-position: center top;
  background-size: cover;
  background-repeat: no-repeat;
  background-attachment: fixed;
}

/* 键盘快速访问无障碍入口 */
.skip-link {
  position: absolute;
  top: -60px;
  left: 20px;
  background: var(--color-primary);
  color: #ffffff;
  padding: 12px 20px;
  z-index: 9999;
  text-decoration: none;
  font-weight: 600;
  border-radius: var(--radius-sm);
  transition: top 0.2s ease;
}

.skip-link:focus {
  top: 15px;
  outline: 3px solid #ffffff;
}

/* 通用容器 */
.container {
  width: 100%;
  max-width: var(--container-max-width);
  margin-left: auto;
  margin-right: auto;
  padding-left: 20px;
  padding-right: 20px;
}

/* 头部导航栏 */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: rgba(10, 14, 23, 0.82);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--color-border);
  height: var(--header-height);
  display: flex;
  align-items: center;
}

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

.brand-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: #ffffff;
  font-size: 1.35rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.brand-icon {
  width: 32px;
  height: 32px;
  border-radius: var(--radius-sm);
  display: block;
  object-fit: cover;
}

.site-nav {
  display: flex;
  align-items: center;
  gap: 24px;
}

.nav-links {
  display: flex;
  list-style: none;
  gap: 20px;
  align-items: center;
}

.nav-links a {
  color: var(--color-text-muted);
  text-decoration: none;
  font-size: 0.95rem;
  font-weight: 500;
  padding: 8px 12px;
  border-radius: var(--radius-sm);
  transition: color var(--transition-normal);
}

.nav-links a:hover,
.nav-links a:focus-visible {
  color: #ffffff;
  outline: 2px solid var(--color-border-focus);
}

/* 按钮通用规范 (触控区域 >= 44x44px) */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 46px;
  min-width: 44px;
  padding: 10px 24px;
  font-size: 1rem;
  font-weight: 600;
  border-radius: var(--radius-sm);
  text-decoration: none;
  cursor: pointer;
  transition: all var(--transition-normal);
  border: 1px solid transparent;
  text-align: center;
}

.btn-primary {
  background: var(--color-accent-gradient);
  color: #ffffff;
  box-shadow: 0 4px 14px rgba(6, 182, 212, 0.35);
}

.btn-primary:hover,
.btn-primary:focus-visible {
  opacity: 0.92;
  box-shadow: 0 6px 20px rgba(6, 182, 212, 0.5);
  transform: translateY(-1px);
  outline: 2px solid #ffffff;
}

.btn-outline {
  background: transparent;
  color: var(--color-text-main);
  border-color: var(--color-border);
}

.btn-outline:hover,
.btn-outline:focus-visible {
  background: var(--color-bg-card-hover);
  border-color: var(--color-primary-light);
  outline: 2px solid var(--color-border-focus);
}

/* 锚点滚动留白 */
section[id] {
  scroll-margin-top: calc(var(--header-height) + 20px);
}

/* Hero 主视觉区 - 清澈通透，标题鲜明高亮 */
.hero-section {
  position: relative;
  padding: 105px 0 85px;
  text-align: center;
  background: transparent;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 18px;
  background-color: rgba(59, 130, 246, 0.15);
  border: 1px solid rgba(59, 130, 246, 0.35);
  border-radius: 9999px;
  font-size: 0.875rem;
  color: var(--color-primary-light);
  margin-bottom: 24px;
}

.hero-title {
  font-size: clamp(2rem, 5vw, 3.25rem);
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 20px;
  letter-spacing: -0.03em;
  color: #ffffff;
}

.text-gradient {
  background: var(--color-accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-subtitle {
  font-size: clamp(1.05rem, 2.5vw, 1.25rem);
  color: #e5e7eb;
  max-width: 780px;
  margin: 0 auto 36px;
  line-height: 1.7;
}

.hero-cta-group {
  display: flex;
  justify-content: center;
  gap: 16px;
  flex-wrap: wrap;
  margin-bottom: 40px;
}

.hero-features-strip {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 32px;
  padding-top: 24px;
  border-top: 1px solid rgba(46, 56, 77, 0.5);
  color: var(--color-text-muted);
  font-size: 0.9rem;
}

.hero-features-strip span {
  display: inline-flex;
  align-items: center;
  gap: 8px;
}

/* 区块通用结构 */
.section {
  padding: 80px 0;
}

.section-alt {
  background-color: var(--color-bg-secondary);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}

.section-header {
  text-align: center;
  max-width: 760px;
  margin: 0 auto 50px;
}

.section-header h2 {
  font-size: clamp(1.75rem, 3.5vw, 2.35rem);
  font-weight: 700;
  margin-bottom: 14px;
  color: #ffffff;
}

.section-header p {
  color: var(--color-text-muted);
  font-size: 1.05rem;
}

/* 核心优势卡片 (3个图文卡片) */
.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 28px;
}

.feature-card {
  background-color: var(--color-bg-card);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 32px 28px;
  transition: transform var(--transition-normal), border-color var(--transition-normal);
  display: flex;
  flex-direction: column;
}

.feature-card:hover {
  transform: translateY(-4px);
  border-color: var(--color-primary);
  background-color: var(--color-bg-card-hover);
}

.feature-icon-wrapper {
  width: 56px;
  height: 56px;
  border-radius: var(--radius-sm);
  background: rgba(59, 130, 246, 0.15);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 22px;
  color: var(--color-primary-light);
}

.feature-card h3 {
  font-size: 1.35rem;
  margin-bottom: 12px;
  color: #ffffff;
}

.feature-card p {
  color: var(--color-text-muted);
  font-size: 0.95rem;
  line-height: 1.7;
}

/* 流媒体与 AI 支持图卡 */
.media-ai-container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 30px;
}

.media-ai-card {
  background-color: var(--color-bg-card);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 36px 30px;
}

.media-ai-card h3 {
  font-size: 1.4rem;
  color: #ffffff;
  margin-bottom: 14px;
  display: flex;
  align-items: center;
  gap: 10px;
}

.media-ai-card p {
  color: var(--color-text-muted);
  font-size: 0.95rem;
  margin-bottom: 24px;
}

.tags-list {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.tag-item {
  background-color: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(255, 255, 255, 0.12);
  padding: 8px 14px;
  border-radius: 9999px;
  font-size: 0.875rem;
  color: #e5e7eb;
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

/* 套餐价格对比表 (语义化表格与自适应横向滚动) */
.pricing-wrapper {
  background-color: var(--color-bg-card);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  overflow-x: auto;
  box-shadow: var(--shadow-card);
}

.pricing-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  min-width: 680px;
}

.pricing-table caption {
  padding: 20px;
  font-size: 1.15rem;
  font-weight: 700;
  color: #ffffff;
  text-align: left;
  border-bottom: 1px solid var(--color-border);
}

.pricing-table th,
.pricing-table td {
  padding: 20px 24px;
  border-bottom: 1px solid var(--color-border);
  vertical-align: middle;
}

.pricing-table thead th {
  background-color: rgba(255, 255, 255, 0.03);
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.pricing-table tbody tr:hover {
  background-color: rgba(255, 255, 255, 0.02);
}

.plan-name {
  font-weight: 700;
  font-size: 1.1rem;
  color: #ffffff;
  display: block;
}

.plan-badge {
  display: inline-block;
  padding: 2px 8px;
  font-size: 0.75rem;
  border-radius: 4px;
  background: var(--color-primary);
  color: #ffffff;
  margin-top: 4px;
}

.plan-price {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--color-accent);
}

.plan-period {
  font-size: 0.85rem;
  color: var(--color-text-subtle);
}

/* 用户评价 */
.reviews-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 24px;
}

.review-card {
  background-color: var(--color-bg-card);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 26px;
}

.stars {
  color: var(--color-warning);
  font-size: 1.1rem;
  margin-bottom: 12px;
}

.review-content {
  font-size: 0.95rem;
  color: var(--color-text-muted);
  line-height: 1.6;
  margin-bottom: 18px;
}

.reviewer-meta {
  display: flex;
  align-items: center;
  gap: 12px;
}

.reviewer-avatar {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: var(--color-bg-secondary);
  border: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  color: var(--color-primary-light);
}

.reviewer-name {
  font-weight: 600;
  color: #ffffff;
  font-size: 0.9rem;
}

.reviewer-title {
  font-size: 0.8rem;
  color: var(--color-text-subtle);
}

/* FAQ 常见问题解答 (原生 details/summary，无需 JS，默认展开) */
.faq-list {
  display: flex;
  flex-direction: column;
  gap: 16px;
  max-width: 860px;
  margin: 0 auto;
}

.faq-item {
  background-color: var(--color-bg-card);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  overflow: hidden;
  transition: border-color var(--transition-normal);
}

.faq-item[open] {
  border-color: var(--color-primary);
}

.faq-question {
  padding: 20px 24px;
  font-size: 1.1rem;
  font-weight: 600;
  color: #ffffff;
  cursor: pointer;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
  user-select: none;
}

.faq-question::-webkit-details-marker {
  display: none;
}

.faq-question::after {
  content: "+";
  font-size: 1.4rem;
  font-weight: 400;
  color: var(--color-text-muted);
  transition: transform 0.2s ease;
}

.faq-item[open] .faq-question::after {
  content: "−";
  color: var(--color-accent);
}

.faq-answer {
  padding: 0 24px 22px;
  color: var(--color-text-muted);
  font-size: 0.95rem;
  line-height: 1.7;
  border-top: 1px solid rgba(255, 255, 255, 0.05);
  padding-top: 16px;
}

.faq-answer a {
  color: var(--color-primary-light);
  text-decoration: underline;
}

/* 页脚：严格只保留四个标题入口，半透明质感，划到底部依然能透视背景图 */
.site-footer {
  margin-top: auto;
  background-color: rgba(6, 9, 15, 0.72);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-top: 1px solid var(--color-border);
  padding: 40px 0 30px;
}

.footer-nav {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 32px;
  flex-wrap: wrap;
  margin-bottom: 24px;
}

.footer-nav a {
  color: var(--color-text-muted);
  text-decoration: none;
  font-size: 1rem;
  font-weight: 500;
  padding: 6px 12px;
  border-radius: var(--radius-sm);
  transition: color var(--transition-normal);
}

.footer-nav a:hover,
.footer-nav a:focus-visible {
  color: #ffffff;
  text-decoration: underline;
  outline: 2px solid var(--color-border-focus);
}

.footer-copyright {
  text-align: center;
  color: var(--color-text-subtle);
  font-size: 0.85rem;
}

/* 知识科普与文章通用样式 - 磨砂通透衬底保证长文阅读体验 */
.article-container {
  max-width: 860px;
  margin: 40px auto 60px;
  padding: 36px 32px;
  background-color: rgba(17, 24, 39, 0.72);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
}

.article-header {
  margin-bottom: 36px;
  border-bottom: 1px solid var(--color-border);
  padding-bottom: 24px;
}

.article-header h1 {
  font-size: clamp(1.8rem, 4vw, 2.4rem);
  font-weight: 800;
  line-height: 1.3;
  color: #ffffff;
  margin-bottom: 16px;
}

.article-meta {
  display: flex;
  gap: 16px;
  color: var(--color-text-subtle);
  font-size: 0.9rem;
}

.article-body {
  font-size: 1.05rem;
  line-height: 1.8;
  color: #d1d5db;
}

.article-body h2 {
  font-size: 1.5rem;
  color: #ffffff;
  margin: 36px 0 16px;
  padding-bottom: 8px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}

.article-body h3 {
  font-size: 1.25rem;
  color: #ffffff;
  margin: 28px 0 12px;
}

.article-body p {
  margin-bottom: 20px;
}

.article-body ul, .article-body ol {
  margin: 0 0 24px 28px;
}

.article-body li {
  margin-bottom: 8px;
}

.article-body blockquote {
  border-left: 4px solid var(--color-primary);
  background: var(--color-bg-card);
  padding: 16px 20px;
  margin: 24px 0;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  color: var(--color-text-muted);
}

.article-body a {
  color: var(--color-primary-light);
  text-decoration: underline;
}

.article-body a:hover {
  color: var(--color-accent);
}

.breadcrumb-nav {
  display: flex;
  gap: 8px;
  align-items: center;
  font-size: 0.875rem;
  color: var(--color-text-subtle);
  margin-bottom: 20px;
}

.breadcrumb-nav a {
  color: var(--color-text-muted);
  text-decoration: none;
}

.breadcrumb-nav a:hover {
  color: #ffffff;
  text-decoration: underline;
}

/* 响应式适配 */
@media (max-width: 768px) {
  .site-header {
    height: auto;
    padding: 14px 0;
  }

  .nav-container {
    flex-direction: column;
    gap: 14px;
  }

  .site-nav {
    width: 100%;
    justify-content: space-between;
  }

  .nav-links {
    gap: 8px;
    flex-wrap: wrap;
    justify-content: center;
  }

  .hero-section {
    padding: 50px 0 40px;
  }

  .hero-cta-group {
    flex-direction: column;
    width: 100%;
  }

  .hero-cta-group .btn {
    width: 100%;
  }

  .section {
    padding: 50px 0;
  }

  .pricing-wrapper {
    margin: 0 -10px;
    border-radius: var(--radius-sm);
  }
}

/* 动效适配尊重用户操作系统偏好 */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}