/* === OpenAI 风深色方案 === */

* { margin: 0; padding: 0; box-sizing: border-box; }

:root {
  /* 深色背景层级 */
  --bg: #0a0a0a;
  --bg-soft: #131315;
  --bg-card: #18181b;
  --bg-card-hover: #1f1f23;

  /* 文字层级 */
  --text: #fafafa;
  --text-secondary: #a1a1aa;
  --text-tertiary: #71717a;
  --text-quaternary: #52525b;

  /* 边框 */
  --border: #27272a;
  --border-strong: #3f3f46;

  /* 强调色（深蓝） */
  --accent: #2563eb;
  --accent-deep: #1e40af;
  --accent-glow: rgba(37, 99, 235, 0.18);

  /* 按钮 */
  --btn-primary-bg: #fafafa;
  --btn-primary-text: #0a0a0a;
  --btn-primary-hover: #ffffff;
}

html {
  scroll-behavior: smooth;
  background: var(--bg);
}

body {
  font-family: "Söhne", -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
               "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  /* 微环境光（深蓝氛围） */
  background-image:
    radial-gradient(ellipse at top, rgba(37, 99, 235, 0.06), transparent 55%),
    radial-gradient(ellipse at bottom, rgba(30, 64, 175, 0.04), transparent 55%);
  background-attachment: fixed;
}

a { color: var(--text); text-decoration: none; transition: color 0.15s ease; }
a:hover { color: var(--accent); }

/* === Header === */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(10, 10, 10, 0.7);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid var(--border);
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 32px;
  max-width: 1440px;
  margin: 0 auto;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 17px;
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--text);
}

.logo-mark {
  width: 26px;
  height: 26px;
  background: linear-gradient(135deg, var(--accent), var(--accent-deep));
  border-radius: 7px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 13px;
  font-weight: 700;
  box-shadow: 0 0 24px var(--accent-glow);
}

.main-nav {
  display: flex;
  align-items: center;
  gap: 32px;
}

.main-nav a {
  font-size: 14px;
  color: var(--text-secondary);
  font-weight: 400;
}

.main-nav a:hover { color: var(--text); }

.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 10px 20px;
  border-radius: 100px;
  font-size: 14px;
  font-weight: 500;
  text-decoration: none;
  transition: all 0.15s ease;
  cursor: pointer;
  border: 1px solid transparent;
  white-space: nowrap;
}

.btn-primary {
  background: var(--btn-primary-bg);
  color: var(--btn-primary-text);
}

.btn-primary:hover {
  background: var(--btn-primary-hover);
  color: var(--btn-primary-text);
  transform: translateY(-1px);
}

.btn-ghost {
  background: transparent;
  color: var(--text);
  border-color: var(--border-strong);
}

.btn-ghost:hover {
  background: var(--bg-card);
  color: var(--text);
  border-color: var(--text-tertiary);
}

/* === Container === */
.container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 32px;
}

.wide { max-width: 1440px; }

/* === Hero === */
.hero {
  padding: 140px 0 120px;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -50%;
  left: 50%;
  transform: translateX(-50%);
  width: 800px;
  height: 800px;
  background: radial-gradient(circle, var(--accent-glow), transparent 70%);
  pointer-events: none;
  z-index: 0;
}

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

.hero-eyebrow {
  display: inline-block;
  padding: 6px 14px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 100px;
  font-size: 13px;
  color: var(--text-secondary);
  margin-bottom: 32px;
}

.hero-eyebrow .dot {
  display: inline-block;
  width: 6px;
  height: 6px;
  background: var(--accent);
  border-radius: 50%;
  margin-right: 8px;
  vertical-align: middle;
  box-shadow: 0 0 8px var(--accent);
  animation: pulse 2s infinite;
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}

.hero h1 {
  font-size: 76px;
  line-height: 1.05;
  letter-spacing: -0.025em;
  font-weight: 500;
  color: var(--text);
  max-width: 1100px;
  margin-bottom: 32px;
  text-wrap: balance;
}

/* 英文版极简 brand statement，加大字号撑场 */
[data-current-lang="en"] .hero h1 {
  font-size: 108px;
  letter-spacing: -0.035em;
  font-weight: 600;
  line-height: 1.0;
}

.hero h1 .accent-text {
  background: linear-gradient(135deg, #60a5fa, var(--accent), var(--accent-deep));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  font-weight: 500;
}

.hero-sub {
  font-size: 21px;
  line-height: 1.5;
  color: var(--text-secondary);
  max-width: 720px;
  margin-bottom: 40px;
}

.hero-actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

/* === Section === */
.section {
  padding: 80px 0;
  border-top: 1px solid var(--border);
}

.section-head {
  display: flex;
  justify-content: space-between;
  align-items: end;
  margin-bottom: 48px;
}

.section-title {
  font-size: 40px;
  font-weight: 500;
  letter-spacing: -0.015em;
  line-height: 1.1;
  color: var(--text);
}

.section-link {
  font-size: 15px;
  color: var(--text-secondary);
  display: inline-flex;
  align-items: center;
  gap: 4px;
}

.section-link:hover { color: var(--accent); }

/* === Card grid === */
.card-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
}

.card-grid.cols-2 { grid-template-columns: repeat(2, 1fr); }

.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 20px;
  padding: 32px;
  transition: all 0.2s ease;
  display: flex;
  flex-direction: column;
  min-height: 240px;
  cursor: default;
  position: relative;
  overflow: hidden;
}

.card::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, transparent, rgba(255, 255, 255, 0.02));
  pointer-events: none;
}

.card:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-strong);
  transform: translateY(-2px);
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.4);
}

.card-eyebrow {
  font-size: 13px;
  color: var(--accent);
  margin-bottom: 12px;
  letter-spacing: 0.02em;
  font-weight: 500;
}

.card-title {
  font-size: 22px;
  font-weight: 500;
  line-height: 1.25;
  color: var(--text);
  margin-bottom: 12px;
  letter-spacing: -0.01em;
}

.card-desc {
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.5;
  flex: 1;
}

.card-link {
  margin-top: 16px;
  font-size: 14px;
  color: var(--text-tertiary);
  font-weight: 500;
}

.card-link:hover { color: var(--accent); }

/* === Inline meta === */
.meta-list {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 32px;
}

.meta-item .meta-label {
  font-size: 13px;
  color: var(--text-tertiary);
  margin-bottom: 6px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.meta-item .meta-value {
  font-size: 16px;
  color: var(--text);
  font-weight: 500;
}

/* === Footer === */
.site-footer {
  background: var(--bg-soft);
  border-top: 1px solid var(--border);
  padding: 64px 0 32px;
  margin-top: 80px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 64px;
}

.footer-brand .logo { margin-bottom: 16px; }

.footer-brand p {
  font-size: 14px;
  color: var(--text-secondary);
  max-width: 360px;
  line-height: 1.6;
}

.footer-col h4 {
  font-size: 13px;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 16px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.footer-col ul { list-style: none; }
.footer-col li { margin-bottom: 10px; }
.footer-col a {
  font-size: 14px;
  color: var(--text-secondary);
}
.footer-col a:hover { color: var(--accent); }

.footer-bottom {
  border-top: 1px solid var(--border);
  padding-top: 24px;
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 16px;
  font-size: 13px;
  color: var(--text-quaternary);
}

.footer-bottom a { color: var(--text-tertiary); margin: 0 6px; }
.footer-bottom a:hover { color: var(--accent); }

/* === Responsive === */
@media (max-width: 1024px) {
  .hero h1 { font-size: 60px; }
  [data-current-lang="en"] .hero h1 { font-size: 84px; }
  .card-grid { grid-template-columns: repeat(2, 1fr); }
  .footer-grid { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 768px) {
  .container { padding: 0 20px; }
  .site-header .container { padding: 12px 20px; }
  .main-nav { display: none; }

  .hero { padding: 80px 0 80px; }
  .hero h1 { font-size: 44px; }
  [data-current-lang="en"] .hero h1 { font-size: 56px; }
  .hero-sub { font-size: 18px; }

  .section { padding: 64px 0; }
  .section-title { font-size: 30px; }
  .section-head { flex-direction: column; align-items: start; gap: 12px; }

  .card-grid, .card-grid.cols-2 { grid-template-columns: 1fr; }
  .card { min-height: auto; padding: 24px; }

  .footer-grid { grid-template-columns: 1fr 1fr; gap: 32px; }
  .footer-bottom { flex-direction: column; align-items: start; }
}

@media (max-width: 480px) {
  .hero h1 { font-size: 36px; }
  [data-current-lang="en"] .hero h1 { font-size: 44px; }
  .footer-grid { grid-template-columns: 1fr; }
}

/* === Selection === */
::selection {
  background: var(--accent);
  color: var(--bg);
}

/* === Language switching === */
[data-current-lang="zh"] [data-lang="en"] { display: none; }
[data-current-lang="en"] [data-lang="zh"] { display: none; }

.lang-switch {
  display: inline-flex;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 100px;
  padding: 3px;
  gap: 2px;
}

.lang-btn {
  background: transparent;
  border: none;
  color: var(--text-secondary);
  font-size: 13px;
  font-weight: 500;
  padding: 5px 12px;
  border-radius: 100px;
  cursor: pointer;
  transition: all 0.15s ease;
  font-family: inherit;
  min-width: 36px;
}

.lang-btn:hover {
  color: var(--text);
}

.lang-btn.active {
  background: var(--accent);
  color: white;
  box-shadow: 0 0 12px var(--accent-glow);
}