/* 全局颜色变量与可读性修复 — 保证高对比度 */
:root {
  --bg-main: #ffffff;
  --bg-soft: #F5F7FA;
  --bg-card: #ffffff;
  --bg-footer: #0B1E2E;
  --text-primary: #1F2937;      /* 深灰，正文高可读 */
  --text-title: #0B3B5A;        /* 深蓝，标题强调 */
  --text-secondary: #334155;    /* 辅助文字，依然清晰 */
  --text-footer: #E2E8F0;       /* 浅色文字用于深色底 */
  --text-footer-muted: #CBD5E1;
  --border-light: #D1D9E6;
  --accent: #0B6B8A;           /* 品牌深青，用于链接/按钮，保证对比 */
  --accent-dark: #094C63;
  --btn-text: #ffffff;
  --nav-bg: rgba(255,255,255,0.92);
  --shadow: 0 8px 24px rgba(0,0,0,0.06);
  --font-main: system-ui, -apple-system, "Segoe UI", Roboto, "PingFang SC", "Microsoft YaHei", sans-serif;
  --gradient-banner: linear-gradient(135deg, #0B3B5A 0%, #1A5F7A 50%, #0B6B8A 100%);
  --glass-bg: rgba(255,255,255,0.6);
  --glass-border: rgba(255,255,255,0.25);
  --card-hover-shadow: 0 16px 40px rgba(11,107,138,0.15);
  --transition-base: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="dark"] {
  --bg-main: #0F172A;
  --bg-soft: #1E293B;
  --bg-card: #1E293B;
  --bg-footer: #020617;
  --text-primary: #E2E8F0;
  --text-title: #F8FAFC;
  --text-secondary: #CBD5E1;
  --text-footer: #E2E8F0;
  --text-footer-muted: #94A3B8;
  --border-light: #334155;
  --accent: #38BDF8;
  --accent-dark: #0EA5E9;
  --btn-text: #0B1E2E;
  --nav-bg: rgba(15,23,42,0.9);
  --shadow: 0 8px 24px rgba(0,0,0,0.4);
  --gradient-banner: linear-gradient(135deg, #020617 0%, #0B1E2E 50%, #1A5F7A 100%);
  --glass-bg: rgba(30,41,59,0.6);
  --glass-border: rgba(148,163,184,0.2);
  --card-hover-shadow: 0 16px 40px rgba(56,189,248,0.12);
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font-main);
  background: var(--bg-main);
  color: var(--text-primary);
  line-height: 1.7;
  transition: background 0.3s ease, color 0.3s ease;
  overflow-x: hidden;
}
h1, h2, h3, h4 { color: var(--text-title); font-weight: 600; line-height: 1.3; }
h1 { font-size: 2.4rem; margin-bottom: 1rem; }
h2 { font-size: 2rem; margin: 2rem 0 1rem; border-left: 6px solid var(--accent); padding-left: 1rem; position: relative; }
h2::after {
  content: '';
  position: absolute;
  left: 0;
  bottom: -8px;
  width: 60px;
  height: 2px;
  background: var(--accent);
  opacity: 0.3;
  border-radius: 2px;
}
h3 { font-size: 1.5rem; margin: 1.5rem 0 0.8rem; }
h4 { font-size: 1.2rem; margin: 1rem 0 0.5rem; }
p { margin-bottom: 1rem; color: var(--text-primary); }
a { color: var(--accent); text-decoration: none; font-weight: 500; transition: var(--transition-base); }
a:hover { color: var(--accent-dark); text-decoration: underline; }
img, svg { max-width: 100%; height: auto; display: block; }
.container { max-width: 1280px; margin: 0 auto; padding: 0 1.5rem; }
.btn {
  display: inline-block;
  background: var(--accent);
  color: var(--btn-text);
  padding: 0.7rem 1.8rem;
  border-radius: 40px;
  font-weight: 600;
  transition: var(--transition-base);
  border: none;
  cursor: pointer;
  position: relative;
  overflow: hidden;
  z-index: 1;
}
.btn::before {
  content: '';
  position: absolute;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100%;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.2), transparent);
  transition: left 0.5s;
  z-index: -1;
}
.btn:hover { background: var(--accent-dark); color: #ffffff; text-decoration: none; transform: translateY(-2px); box-shadow: 0 8px 20px rgba(11,107,138,0.25); }
.btn:hover::before { left: 100%; }

/* 导航 */
.navbar {
  position: sticky;
  top: 0;
  z-index: 50;
  background: var(--nav-bg);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border-light);
  transition: background 0.3s;
}
.nav-inner { display: flex; align-items: center; justify-content: space-between; height: 70px; }
.logo { font-size: 1.8rem; font-weight: 700; color: var(--text-title); transition: var(--transition-base); }
.logo span { color: var(--accent); }
.nav-links { display: flex; gap: 2rem; align-items: center; }
.nav-links a { color: var(--text-primary); font-weight: 500; position: relative; padding: 0.5rem 0; }
.nav-links a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--accent);
  transition: width 0.3s;
}
.nav-links a:hover { color: var(--accent); text-decoration: none; }
.nav-links a:hover::after { width: 100%; }
.nav-actions { display: flex; gap: 0.8rem; align-items: center; }
.theme-toggle, .search-toggle { background: none; border: none; font-size: 1.4rem; cursor: pointer; color: var(--text-primary); padding: 0.2rem; transition: var(--transition-base); }
.theme-toggle:hover, .search-toggle:hover { transform: rotate(15deg) scale(1.1); }
.mobile-menu { display: none; background: none; border: none; font-size: 2rem; color: var(--text-primary); cursor: pointer; transition: var(--transition-base); }
.mobile-menu:hover { transform: scale(1.1); }

/* 搜索框 */
.search-wrap {
  display: flex;
  align-items: center;
  border: 1px solid var(--border-light);
  border-radius: 40px;
  overflow: hidden;
  background: var(--bg-card);
  transition: var(--transition-base);
}
.search-wrap:focus-within {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(11,107,138,0.1);
}
.search-wrap input { border: none; padding: 0.5rem 1rem; width: 180px; background: transparent; color: var(--text-primary); outline: none; }
.search-wrap button {
  background: var(--accent);
  border: none;
  color: white;
  padding: 0.5rem 1rem;
  cursor: pointer;
  transition: var(--transition-base);
}
.search-wrap button:hover { background: var(--accent-dark); }

/* banner */
.banner {
  background: var(--gradient-banner);
  padding: 5rem 0;
  color: white;
  position: relative;
  overflow: hidden;
}
.banner::before {
  content: '';
  position: absolute;
  top: -50%;
  right: -20%;
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, rgba(255,255,255,0.1) 0%, transparent 70%);
  animation: float 8s ease-in-out infinite;
}
.banner::after {
  content: '';
  position: absolute;
  bottom: -50%;
  left: -20%;
  width: 400px;
  height: 400px;
  background: radial-gradient(circle, rgba(255,255,255,0.08) 0%, transparent 70%);
  animation: float 6s ease-in-out infinite reverse;
}
@keyframes float {
  0%, 100% { transform: translateY(0) rotate(0deg); }
  50% { transform: translateY(-20px) rotate(5deg); }
}
.banner h1 { color: #ffffff; position: relative; z-index: 1; animation: fadeInRight 0.8s ease; }
.banner p { color: #E2E8F0; font-size: 1.2rem; max-width: 700px; position: relative; z-index: 1; animation: fadeInRight 0.8s ease 0.2s both; }
.banner .btn { background: #F59E0B; color: #0B1E2E; position: relative; z-index: 1; animation: fadeInRight 0.8s ease 0.4s both; }
.banner .btn:hover { background: #F59E0B; transform: translateY(-2px) scale(1.02); box-shadow: 0 10px 25px rgba(245,158,11,0.3); }

@keyframes fadeInRight {
  from { opacity: 0; transform: translateX(30px); }
  to { opacity: 1; transform: translateX(0); }
}

/* 卡片 */
.card-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 1.8rem; margin: 2rem 0; }
.card {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: 16px;
  padding: 1.8rem;
  box-shadow: var(--shadow);
  transition: var(--transition-base);
  position: relative;
  overflow: hidden;
}
.card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 3px;
  background: linear-gradient(90deg, var(--accent), transparent);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.4s;
}
.card:hover {
  transform: translateY(-8px);
  box-shadow: var(--card-hover-shadow);
  border-color: var(--accent);
}
.card:hover::before { transform: scaleX(1); }
.card h3 { margin-bottom: 0.5rem; transition: var(--transition-base); }
.card:hover h3 { color: var(--accent); }
.card p { color: var(--text-secondary); }

/* 文章列表 */
.article-list { display: flex; flex-direction: column; gap: 1.2rem; }
.article-item {
  border-bottom: 1px solid var(--border-light);
  padding-bottom: 1.2rem;
  transition: var(--transition-base);
  padding: 1rem;
  border-radius: 8px;
}
.article-item:hover {
  background: var(--bg-soft);
  padding-left: 1.5rem;
  border-color: var(--accent);
}
.article-item h4 { margin-bottom: 0.3rem; transition: var(--transition-base); }
.article-item:hover h4 { color: var(--accent); }
.article-meta { font-size: 0.9rem; color: var(--text-secondary); }

/* FAQ */
.faq-item {
  border-bottom: 1px solid var(--border-light);
  padding: 1rem 0;
  transition: var(--transition-base);
}
.faq-item:hover { padding-left: 0.5rem; }
.faq-q {
  font-weight: 600;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  color: var(--text-title);
  transition: var(--transition-base);
}
.faq-q:hover { color: var(--accent); }
.faq-q span {
  width: 28px;
  height: 28px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  background: var(--bg-soft);
  color: var(--accent);
  font-size: 1.2rem;
  transition: var(--transition-base);
}
.faq-item:hover .faq-q span { background: var(--accent); color: white; transform: rotate(90deg); }
.faq-a { margin-top: 0.8rem; color: var(--text-primary); animation: fadeIn 0.3s ease; }

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(-10px); }
  to { opacity: 1; transform: translateY(0); }
}

/* 表格、列表 */
table { width: 100%; border-collapse: collapse; margin: 1.5rem 0; }
th, td { border: 1px solid var(--border-light); padding: 0.8rem; text-align: left; transition: var(--transition-base); }
th { background: var(--bg-soft); color: var(--text-title); }
tr:hover td { background: var(--bg-soft); }

/* footer */
footer { background: var(--bg-footer); color: var(--text-footer); padding: 3rem 0 1rem; margin-top: 4rem; position: relative; }
footer::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--accent), transparent);
}
footer a { color: var(--text-footer); transition: var(--transition-base); }
footer a:hover { color: #ffffff; text-decoration: none; padding-left: 5px; }
.footer-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 2rem; }
.footer-grid h4 { color: #ffffff; position: relative; padding-bottom: 0.8rem; }
.footer-grid h4::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 30px;
  height: 2px;
  background: var(--accent);
}
.footer-bottom { border-top: 1px solid #334155; margin-top: 2rem; padding-top: 1.5rem; text-align: center; color: var(--text-footer-muted); }

/* 暗黑模式调整 */
[data-theme="dark"] .banner { background: var(--gradient-banner); }
[data-theme="dark"] .banner h1 { color: #F8FAFC; }
[data-theme="dark"] .banner p { color: #CBD5E1; }
[data-theme="dark"] .card { background: var(--bg-card); }
[data-theme="dark"] .search-wrap input { color: var(--text-primary); }

.back-to-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  background: var(--accent);
  color: white;
  border: none;
  border-radius: 50%;
  width: 48px;
  height: 48px;
  font-size: 1.8rem;
  cursor: pointer;
  box-shadow: 0 4px 12px rgba(0,0,0,0.2);
  z-index: 100;
  transition: var(--transition-base);
  opacity: 0;
  visibility: hidden;
  transform: translateY(20px);
}
.back-to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}
.back-to-top:hover { background: var(--accent-dark); transform: translateY(-5px); box-shadow: 0 8px 20px rgba(0,0,0,0.3); }

/* 移动端 */
@media (max-width: 768px) {
  h1 { font-size: 2rem; }
  h2 { font-size: 1.6rem; }
  h3 { font-size: 1.3rem; }
  
  .nav-links {
    display: none;
    flex-direction: column;
    position: absolute;
    top: 70px;
    left: 0;
    right: 0;
    background: var(--bg-main);
    padding: 1rem;
    gap: 1rem;
    border-bottom: 1px solid var(--border-light);
    box-shadow: var(--shadow);
    animation: slideDown 0.3s ease;
  }
  .nav-links.active { display: flex; }
  .nav-links a { padding: 0.8rem 0; border-bottom: 1px solid var(--border-light); }
  .nav-links a:last-child { border-bottom: none; }
  .nav-links a::after { display: none; }
  
  @keyframes slideDown {
    from { opacity: 0; transform: translateY(-10px); }
    to { opacity: 1; transform: translateY(0); }
  }
  
  .mobile-menu { display: block; }
  .search-wrap input { width: 100px; }
  .search-wrap { max-width: 200px; }
  .footer-grid { grid-template-columns: 1fr 1fr; gap: 1.5rem; }
  .banner { padding: 3rem 0; }
  .banner p { font-size: 1rem; }
  .back-to-top { bottom: 1.5rem; right: 1.5rem; width: 40px; height: 40px; font-size: 1.5rem; }
}

@media (max-width: 480px) {
  .footer-grid { grid-template-columns: 1fr; }
  .card-grid { grid-template-columns: 1fr; }
  .nav-actions { gap: 0.5rem; }
  .search-wrap input { width: 80px; }
  .container { padding: 0 1rem; }
}

/* 滚动动画 */
.card, .article-item, .faq-item, .banner .btn {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}
.card.visible, .article-item.visible, .faq-item.visible, .banner .btn.visible {
  opacity: 1;
  transform: translateY(0);
}

/* 玻璃拟态效果 */
.glass-effect {
  background: var(--glass-bg);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border: 1px solid var(--glass-border);
  border-radius: 16px;
}

/* 自定义滚动条 */
::-webkit-scrollbar {
  width: 10px;
}
::-webkit-scrollbar-track {
  background: var(--bg-soft);
}
::-webkit-scrollbar-thumb {
  background: var(--accent);
  border-radius: 5px;
  transition: var(--transition-base);
}
::-webkit-scrollbar-thumb:hover {
  background: var(--accent-dark);
}

/* 选中文本样式 */
::selection {
  background: var(--accent);
  color: white;
}

/* 链接下划线动画 */
a:not(.btn):not(.logo) {
  position: relative;
}
a:not(.btn):not(.logo)::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  width: 0;
  height: 1px;
  background: var(--accent);
  transition: width 0.3s;
}
a:not(.btn):not(.logo):hover::after {
  width: 100%;
}

/* 块引用样式 */
blockquote {
  border-left: 4px solid var(--accent);
  padding-left: 1rem;
  color: var(--text-secondary);
  position: relative;
  background: var(--bg-soft);
  padding: 1rem 1.5rem;
  border-radius: 0 8px 8px 0;
  transition: var(--transition-base);
}
blockquote:hover {
  border-left-width: 6px;
  background: var(--bg-card);
}

/* 列表样式 */
ul, ol {
  margin-left: 1.2rem;
  margin-bottom: 1rem;
}
li {
  margin-bottom: 0.5rem;
  padding-left: 0.5rem;
  position: relative;
}
ul li::before {
  content: '▸';
  position: absolute;
  left: -1rem;
  color: var(--accent);
}

/* 图片悬浮效果 */
img {
  transition: var(--transition-base);
}
img:hover {
  transform: scale(1.02);
  box-shadow: var(--shadow);
}

/* 表单焦点样式 */
input:focus, button:focus {
  outline: none;
  box-shadow: 0 0 0 3px rgba(11,107,138,0.15);
}