/* === Reset & Variables === */
*, *::before, *::after { margin:0; padding:0; box-sizing:border-box; }
:root {
  --color-deep-blue: #0B1A2E;
  --color-gold: #F2C94C;
  --color-red: #E63946;
  --color-white: #FFFFFF;
  --color-gray-1: #B0B8C1;
  --color-gray-2: #2C3E50;
  --color-gold-red-gradient: linear-gradient(135deg, #F2C94C, #E63946);
  --color-transparent-blue: rgba(11,26,46,0.7);
  --font-heading: 'Inter','Helvetica','Arial',sans-serif;
  --font-body: 'Inter','Noto Sans SC','Microsoft YaHei',sans-serif;
  --font-data: 'JetBrains Mono','Consolas',monospace;
  --max-width: 1200px;
  --header-height: 60px;
  --focus-glow: 0 0 0 3px var(--color-gold);
  --card-radius: 12px;
}
html { scroll-behavior: smooth; }
body {
  background: var(--color-deep-blue);
  color: var(--color-white);
  font-family: var(--font-body);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--color-gold); text-decoration: none; transition: color 0.2s; }
a:hover { color: var(--color-red); }
a:focus-visible { outline: none; box-shadow: var(--focus-glow); border-radius: 4px; }
:focus-visible { outline: none; box-shadow: var(--focus-glow); }
::selection { background: var(--color-gold); color: var(--color-deep-blue); }
img, svg { max-width: 100%; display: block; }
ul, ol { list-style: none; }
button { cursor: pointer; font-family: inherit; border: none; background: none; color: inherit; }

/* === Skip Link === */
.skip-link {
  position: absolute; z-index: 10000; top: -100%; left: 1rem; padding: 0.5rem 1rem;
  background: var(--color-gold); color: var(--color-deep-blue); font-weight: bold;
  border-radius: 0 0 6px 6px; transition: top 0.3s;
}
.skip-link:focus { top: 0; }

/* === Header === */
.site-header {
  position: sticky; top: 0; z-index: 999; background: var(--color-deep-blue);
  border-bottom: 2px solid var(--color-gray-2); height: var(--header-height);
}
.header-inner {
  max-width: var(--max-width); margin: 0 auto; display: flex; align-items: center;
  justify-content: space-between; height: 100%; padding: 0 1.5rem;
}
.logo {
  font-family: var(--font-heading); font-weight: 800; font-size: 1.5rem;
  letter-spacing: 0.05em; color: var(--color-gold); text-transform: uppercase;
  flex-shrink: 0;
}
.nav-toggle { display: none; flex-direction: column; gap: 5px; padding: 0.25rem; }
.nav-toggle-bar {
  display: block; width: 24px; height: 2px; background: var(--color-white);
  border-radius: 2px; transition: transform 0.3s, opacity 0.3s;
}
.nav-list ul { display: flex; gap: 1.25rem; align-items: center; }
.nav-list a {
  position: relative; display: inline-block; padding: 0.25rem 0;
  font-family: var(--font-heading); font-weight: 600; font-size: 0.9rem;
  letter-spacing: 0.03em; color: var(--color-white); text-transform: uppercase;
  transition: color 0.2s;
}
.nav-list a:hover { color: var(--color-gold); }
.nav-list a:focus-visible { outline: none; box-shadow: var(--focus-glow); border-radius: 4px; }
/* 当前页面指示器（星空闪烁） */
.nav-list a[aria-current="page"] {
  color: var(--color-gold);
}
.nav-list a[aria-current="page"]::after {
  content: ''; position: absolute; bottom: -2px; left: 50%; transform: translateX(-50%);
  width: 8px; height: 8px; background: radial-gradient(circle, var(--color-gold) 40%, transparent 70%);
  border-radius: 50%; opacity: 0.9;
  animation: star-pulse 2s ease-in-out infinite;
}
@keyframes star-pulse {
  0%, 100% { opacity: 0.4; transform: translateX(-50%) scale(0.8); }
  50% { opacity: 1; transform: translateX(-50%) scale(1.1); }
}
@media (prefers-reduced-motion: reduce) {
  .nav-list a[aria-current="page"]::after { animation: none; opacity: 0.7; }
}
/* 移动端导航 */
@media (max-width: 768px) {
  .nav-toggle { display: flex; }
  .nav-list {
    position: fixed; top: var(--header-height); left: 0; right: 0;
    background: var(--color-gray-2); padding: 1rem 1.5rem; transform: translateY(-120%);
    transition: transform 0.35s ease; box-shadow: 0 8px 16px rgba(0,0,0,0.5);
    z-index: 998;
  }
  .nav-list[data-open] { transform: translateY(0); }
  .nav-list ul { flex-direction: column; gap: 0.75rem; }
  .nav-list a { display: block; padding: 0.5rem 0; font-size: 1rem; }
  .header-inner { padding: 0 1rem; }
}

/* === Footer === */
.site-footer {
  background: var(--color-gray-2); border-top: 2px solid var(--color-gold);
  padding: 2.5rem 1.5rem 1.5rem;
}
.footer-inner {
  max-width: var(--max-width); margin: 0 auto; display: flex; flex-wrap: wrap;
  justify-content: space-between; gap: 1.5rem;
}
.footer-brand {
  font-family: var(--font-heading); font-weight: 800; font-size: 1.25rem;
  color: var(--color-gold); letter-spacing: 0.05em; flex: 1 1 100%;
  text-align: center; margin-bottom: 0.5rem;
}
.footer-links { display: flex; flex-wrap: wrap; gap: 1rem; justify-content: center; width: 100%; }
.footer-links a { font-size: 0.9rem; padding: 0.25rem 0.5rem; border-radius: 6px; transition: background 0.2s; }
.footer-links a:hover { background: var(--color-transparent-blue); }
.footer-contact { width: 100%; text-align: center; color: var(--color-gray-1); font-size: 0.85rem; }
.footer-icp { width: 100%; text-align: center; color: var(--color-gray-1); font-size: 0.8rem; }
.footer-copy { width: 100%; text-align: center; margin-top: 1rem; color: var(--color-gray-1); font-size: 0.8rem; }
@media (min-width: 600px) {
  .footer-brand { flex: 0 0 auto; text-align: left; margin-bottom: 0; }
  .footer-links { flex: 1; justify-content: flex-end; width: auto; }
  .footer-contact, .footer-icp, .footer-copy { text-align: right; }
}

/* === Back to Top === */
.back-to-top {
  position: fixed; bottom: 2rem; right: 2rem; z-index: 9999;
  width: 48px; height: 48px; border-radius: 50%; background: var(--color-gold);
  color: var(--color-deep-blue); font-size: 1.5rem; font-weight: bold;
  display: flex; align-items: center; justify-content: center;
  box-shadow: 0 4px 12px rgba(0,0,0,0.4); opacity: 0; visibility: hidden;
  transform: translateY(20px); transition: opacity 0.3s, visibility 0.3s, transform 0.3s;
}
.back-to-top.show { opacity: 1; visibility: visible; transform: translateY(0); }
.back-to-top:hover { background: var(--color-red); color: var(--color-white); }
.back-to-top:focus-visible { outline: none; box-shadow: var(--focus-glow); }
@media (prefers-reduced-motion: reduce) {
  .back-to-top { transition: none; }
}

/* === Global Components === */
.btn {
  display: inline-block; padding: 0.65rem 1.5rem; border-radius: 8px;
  font-family: var(--font-heading); font-weight: 700; font-size: 0.95rem;
  letter-spacing: 0.05em; text-transform: uppercase; text-align: center;
  background: var(--color-gold); color: var(--color-deep-blue);
  transition: background 0.25s, color 0.25s, box-shadow 0.25s;
}
.btn:hover { background: var(--color-red); color: var(--color-white); box-shadow: 0 4px 16px rgba(230,57,70,0.4); }
.btn:focus-visible { box-shadow: var(--focus-glow); }

.card {
  background: var(--color-transparent-blue); border: 1px solid var(--color-gray-2);
  border-radius: var(--card-radius); padding: 1.5rem; backdrop-filter: blur(6px);
  transition: transform 0.25s, box-shadow 0.25s;
}
.card:hover { transform: translateY(-4px); box-shadow: 0 8px 24px rgba(0,0,0,0.4); }
.card:focus-within { box-shadow: var(--focus-glow); }
@media (prefers-reduced-motion: reduce) {
  .card:hover { transform: none; }
}

.section-title {
  font-family: var(--font-heading); font-weight: 800; font-size: 2rem;
  letter-spacing: 0.05em; margin-bottom: 0.75rem; display: flex; align-items: baseline; gap: 0.5rem;
}
.section-title span { color: var(--color-gold); font-size: 2.5rem; margin-right: 0.25rem; }
.section-title strong { color: var(--color-white); }
.section-desc { color: var(--color-gray-1); font-size: 1rem; max-width: 720px; margin-bottom: 2rem; }

.data-value {
  font-family: var(--font-data); font-weight: 500; font-size: 1.25rem;
  color: var(--color-gold);
}
.data-value.highlight { color: var(--color-red); }

/* === Grid System === */
.grid-2, .grid-3, .grid-4 {
  display: grid; gap: 1.5rem;
}
.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }
@media (max-width: 900px) {
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .grid-3 { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 600px) {
  .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }
}

/* === Content Container === */
.content-container {
  max-width: var(--max-width); margin: 0 auto; padding: 2rem 1.5rem;
}

/* === Fade-in (配合 JS IntersectionObserver) === */
.fade-in-section { opacity: 0; transform: translateY(20px); transition: opacity 0.5s, transform 0.5s; }
.fade-in-section.is-visible { opacity: 1; transform: translateY(0); }
@media (prefers-reduced-motion: reduce) {
  .fade-in-section { opacity: 1; transform: none; transition: none; }
}

/* === Responsive Helpers === */
@media (max-width: 480px) {
  .section-title { font-size: 1.5rem; }
  .section-title span { font-size: 2rem; }
}