/* ===== CSS变量 ===== */
:root {
  --navy: #051830; --navy-light: #0a2d52; --blue: #1d4ed8; --blue-bright: #2563eb;
  --blue-pale: #eff6ff; --white: #ffffff; --bg: #f8fafc;
  --text: #0f172a; --text-2: #475569; --text-3: #64748b;
  --border: #e2e8f0; --border-light: #f1f5f9;
  --shadow-card: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
  --shadow-hover: 0 10px 40px rgba(0,0,0,0.1), 0 1px 3px rgba(0,0,0,0.05);
  --shadow-lg: 0 20px 60px rgba(0,0,0,0.12);
}

/* ===== 全局重置 ===== */
* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

body {
  background: var(--white); color: var(--text);
  font-family: 'DM Sans', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  font-size: 17px; font-weight: 500; line-height: 1.68;
  -webkit-font-smoothing: antialiased; overflow-x: hidden; letter-spacing: -0.01em;
}

h1, h2, h3, .font-display {
  font-family: 'Playfair Display', 'Noto Serif SC', 'STSong', serif;
  font-weight: 800; letter-spacing: -0.02em;
}

/* ===== Eyebrow ===== */
.eyebrow {
  display: inline-flex; align-items: center; gap: 0.6rem;
  font-size: 0.78rem; font-weight: 700; letter-spacing: 0.28em;
  color: var(--blue); text-transform: uppercase; margin-bottom: 1rem;
  font-family: 'DM Sans', sans-serif;
}
.eyebrow::before { content: ''; display: block; width: 20px; height: 2.5px; background: var(--blue-bright); border-radius: 2px; }

/* ===== 导航栏 ===== */
#navbar {
  position: fixed; top: 0; left: 0; right: 0; z-index: 50;
  height: 86px; display: flex; align-items: center; justify-content: space-between;
  padding: 0 3rem;
  background: rgba(255,255,255,0.94);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid var(--border-light);
  transition: box-shadow 0.4s, height 0.4s;
}
#navbar.scrolled { box-shadow: 0 2px 20px rgba(0,0,0,0.06); height: 68px; }

.nav-link {
  color: var(--text-2); font-size: 1.05rem; font-weight: 700;
  letter-spacing: 0.05em; text-decoration: none;
  padding: 0.4rem 0; transition: color 0.3s; position: relative;
}
.nav-link:hover, .nav-link.active { color: var(--navy); }
.nav-link::after {
  content: ''; position: absolute; bottom: -6px; left: 50%; transform: translateX(-50%) scaleX(0);
  width: 100%; height: 3px; border-radius: 2px;
  background: linear-gradient(90deg, var(--navy), var(--blue-bright));
  transition: transform 0.4s cubic-bezier(0.22,0.61,0.36,1);
}
.nav-link:hover::after, .nav-link.active::after { transform: translateX(-50%) scaleX(1); }

.logo-box {
  width: 46px; height: 46px; border-radius: 12px;
  display: flex; align-items: center; justify-content: center;
  background: linear-gradient(135deg, var(--navy), var(--navy-light));
  color: #fff; font-size: 1.3rem;
}

/* ===== 移动菜单 ===== */
#mobile-menu {
  position: fixed; inset: 0; z-index: 45;
  background: rgba(255,255,255,0.97); backdrop-filter: blur(20px);
  display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 2rem;
  opacity: 0; visibility: hidden; transition: opacity 0.35s, visibility 0.35s;
}
#mobile-menu.open { opacity: 1; visibility: visible; }

/* ===== 子页 Hero ===== */
.page-hero {
  position: relative; padding: 140px 0 80px; overflow: hidden;
  background: linear-gradient(160deg, #031525 0%, #051d36 35%, #082848 70%, #0a2d52 100%);
}
.hero-dots {
  position: absolute; inset: 0; opacity: 0.06;
  background-image: radial-gradient(circle at 30% 40%, #fff 2px, transparent 2px),
                    radial-gradient(circle at 70% 60%, #fff 1.5px, transparent 1.5px);
  background-size: 90px 90px, 70px 70px;
}
.hero-glow {
  position: absolute; width: 600px; height: 600px; border-radius: 50%; filter: blur(140px); pointer-events: none;
  background: radial-gradient(circle, rgba(37,99,235,0.18) 0%, transparent 65%);
  top: -10%; right: -5%;
}
.page-hero-title { font-size: clamp(2.8rem, 6vw, 5rem); line-height: 1.1; color: #fff; font-weight: 900; }

/* ===== 按钮 ===== */
.btn {
  display: inline-flex; align-items: center; gap: 0.5rem;
  padding: 1rem 2.6rem; border-radius: 8px;
  font-weight: 700; font-size: 0.95rem; letter-spacing: 0.04em;
  text-decoration: none; cursor: pointer; transition: all 0.3s ease;
}
.btn-primary {
  background: var(--blue-bright); color: #fff; border: none;
  box-shadow: 0 4px 14px rgba(37,99,235,0.35);
}
.btn-primary:hover { background: #1d4ed8; transform: translateY(-2px); box-shadow: 0 8px 28px rgba(37,99,235,0.45); }

/* ===== 卡片 ===== */
.card {
  background: var(--white); border: 1px solid var(--border);
  border-radius: 16px; box-shadow: var(--shadow-card);
  transition: transform 0.45s cubic-bezier(0.22,0.61,0.36,1), box-shadow 0.45s, border-color 0.45s;
}
.card:hover { transform: translateY(-6px); border-color: #cbd5e1; box-shadow: var(--shadow-hover); }

/* ===== 滚动揭示动画 ===== */
.reveal { opacity: 0; transform: translateY(40px); transition: opacity 0.8s cubic-bezier(0.22,0.61,0.36,1), transform 0.8s cubic-bezier(0.22,0.61,0.36,1); }
.reveal.visible { opacity: 1; transform: translateY(0); }

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(40px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ===== 工具类 ===== */
.bg-alt { background: var(--bg); }
.bg-navy { background: var(--navy); color: #fff; }
.kw-tag {
  display: inline-block; padding: 0.15rem 0.5rem; border-radius: 3px;
  font-size: 0.75rem; font-weight: 700;
  background: var(--blue-pale); color: var(--blue);
}
.kw-tag-dark {
  display: inline-block; padding: 0.15rem 0.5rem; border-radius: 3px;
  font-size: 0.75rem; font-weight: 700;
  background: rgba(37,99,235,0.15); color: #93c5fd;
}

/* ===== 返回顶部 ===== */
#back-top {
  position: fixed; bottom: 34px; right: 34px; z-index: 40;
  width: 48px; height: 48px; border-radius: 50%;
  background: var(--navy); border: none; cursor: pointer;
  display: flex; align-items: center; justify-content: center;
  opacity: 0; visibility: hidden; transform: translateY(12px);
  transition: all 0.35s ease; color: #fff; font-size: 1rem;
  box-shadow: 0 6px 24px rgba(5,24,48,0.35);
}
#back-top.visible { opacity: 1; visibility: visible; transform: translateY(0); }
#back-top:hover { background: var(--blue-bright); }