:root {
  --bg: #ffffff;
  --bg-2: #f4f5f8;
  --bg-3: #eceef3;
  --text: #0a0a10;
  --text-2: rgba(10, 10, 16, 0.6);
  --text-3: rgba(10, 10, 16, 0.4);
  --grad: linear-gradient(135deg, #6366f1, #a855f7, #ec4899);
  --grad-2: linear-gradient(135deg, #6366f1, #a855f7);
  --radius: 10px;
  --radius-sm: 6px;
  --radius-lg: 12px;
  --maxw: 960px;
  --nav-h: 64px;
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", "Microsoft YaHei", system-ui, sans-serif;
  /* 主题相关（浅色为默认） */
  --nav-bg: rgba(255, 255, 255, 0.85);
  --card-bg: rgba(10, 10, 16, 0.03);
  --card-border: rgba(10, 10, 16, 0.08);
  --border: rgba(10, 10, 16, 0.08);
}

[data-theme="dark"] {
  --bg: #0a0a10;
  --bg-2: #0d0d14;
  --bg-3: #121218;
  --text: #ffffff;
  --text-2: rgba(255, 255, 255, 0.5);
  --text-3: rgba(255, 255, 255, 0.4);
  --nav-bg: rgba(10, 10, 16, 0.85);
  --card-bg: rgba(255, 255, 255, 0.02);
  --card-border: rgba(255, 255, 255, 0.06);
  --border: rgba(255, 255, 255, 0.08);
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  transition: background-color .3s ease, color .3s ease;
}
a { color: inherit; text-decoration: none; }
img { max-width: 100%; display: block; }

.container { max-width: var(--maxw); margin: 0 auto; padding: 0 20px; }

/* ---------- 导航 ---------- */
.nav {
  position: sticky; top: 0; z-index: 100;
  height: var(--nav-h);
  display: flex; align-items: center;
  background: var(--nav-bg);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  transition: background .3s, border-color .3s;
}
.nav.scrolled {
  background: var(--bg);
  border-bottom: 1px solid var(--border);
}
.nav .container { display: flex; align-items: center; justify-content: space-between; width: 100%; }
.nav-right { display: flex; align-items: center; gap: 18px; }
.logo { display: flex; align-items: center; gap: 10px; font-weight: 700; }
.logo .logo-mark {
  width: 34px; height: 34px; border-radius: var(--radius-sm);
  display: block;
  animation: logoIn .6s ease both;
}
.nav-links { display: flex; gap: 28px; align-items: center; }
.nav-links a { color: var(--text-2); font-size: 15px; transition: color .2s; }
.nav-links a:hover, .nav-links a.active { color: var(--text); }
.nav-toggle { display: none; background: none; border: 0; color: var(--text); font-size: 24px; cursor: pointer; line-height: 1; height: 34px; width: 34px; align-items: center; justify-content: center; }
.theme-toggle {
  background: none; border: 0; color: var(--text);
  cursor: pointer; line-height: 1;
  padding: 0; height: 34px; width: 34px; border-radius: 8px; transition: background-color .2s;
  display: inline-flex; align-items: center; justify-content: center;
}
.theme-toggle:hover { background: var(--card-bg); }
.theme-toggle svg { width: 19px; height: 19px; display: block; }
.nav-toggle svg { width: 22px; height: 22px; display: block; }
/* 默认（浅色）：显示月亮（点击切换到深色）；深色模式：显示太阳 */
.theme-toggle .icon-sun { display: none; }
.theme-toggle .icon-moon { display: block; }
[data-theme="dark"] .theme-toggle .icon-sun { display: block; }
[data-theme="dark"] .theme-toggle .icon-moon { display: none; }

/* ---------- 通用区块 ---------- */
section { padding: 80px 0; }
.section--alt { background: var(--bg-2); transition: background-color .3s ease; }
.section--cta {
  background: linear-gradient(160deg, rgba(99, 102, 241, 0.06), transparent);
  text-align: center;
  transition: background-color .3s ease;
}
.section-head { text-align: center; max-width: 600px; margin: 0 auto 44px; }
.section-head .section-sub { margin-bottom: 0; }
.section-title { font-size: 28px; font-weight: 700; margin-bottom: 8px; }
.section-sub { color: var(--text-2); }
.gradient-text {
  background: var(--grad); -webkit-background-clip: text;
  background-clip: text; color: transparent;
}

/* ---------- eyebrow 小标签（方案 C 标识） ---------- */
.eyebrow {
  font-size: 11px;
  letter-spacing: 2px;
  text-transform: uppercase;
  color: var(--text-3);
  margin-bottom: 8px;
}

/* ---------- 分隔线 ---------- */
.divider {
  width: 40px; height: 2px;
  background: var(--grad-2);
  margin: 24px auto;
}

/* ---------- Hero ---------- */
.hero { padding: 100px 0 80px; }
.hero .container { text-align: center; max-width: 600px; }
.hero-icon {
  width: 56px; height: 56px; border-radius: var(--radius-lg);
  background: var(--grad-2);
  display: grid; place-items: center;
  font-size: 24px; font-weight: 800; color: #fff;
  margin: 0 auto 20px;
}
.hero h1 { font-size: 48px; line-height: 1.15; letter-spacing: -1px; margin-bottom: 0; }
.hero p {
  color: var(--text-2); font-size: 15px;
  max-width: 440px; margin: 0 auto 32px; line-height: 1.7;
}
.hero-cta { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }

/* ---------- 按钮 ---------- */
.btn {
  display: inline-block; padding: 11px 28px; border-radius: var(--radius-sm);
  font-weight: 600; font-size: 14px; cursor: pointer; border: 0;
  transition: transform .2s, filter .2s;
}
.btn-primary { background: var(--grad); color: #fff; }
.btn-primary:hover { transform: translateY(-2px); filter: brightness(1.08); }
.btn-ghost { background: var(--bg-3); color: var(--text); border: 1px solid var(--border); transition: transform .2s, filter .2s, border-color .3s, background-color .3s; }
.btn-ghost:hover { transform: translateY(-2px); border-color: #a855f7; }

/* ---------- 卡片 ---------- */
.grid { display: grid; gap: 20px; }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-2 { grid-template-columns: repeat(2, 1fr); }
.card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-lg); padding: 32px 20px;
  transition: transform .25s, border-color .25s, box-shadow .25s, background-color .3s;
}
.card.center { text-align: center; }
.card:hover {
  transform: translateY(-6px);
  border-color: #a855f7;
  box-shadow: 0 12px 30px rgba(168, 85, 247, 0.18);
}
.card h3 { font-size: 17px; margin-bottom: 8px; }
.card p { color: var(--text-2); font-size: 14px; }
.icon-emoji { font-size: 32px; margin-bottom: 12px; line-height: 1; }

/* ---------- 引语 ---------- */
.quote { text-align: center; max-width: 520px; margin: 0 auto; }
.quote .mark {
  font-size: 56px; color: #6366f1; line-height: 1;
  opacity: .5; margin-bottom: 12px;
}
.quote p {
  font-size: 18px; font-style: italic; color: var(--text-2);
  line-height: 1.7; margin-bottom: 16px;
}

/* ---------- 表单 ---------- */
.field { margin-bottom: 18px; }
.field label { display: block; font-size: 14px; color: var(--text-2); margin-bottom: 6px; }
.field input, .field textarea {
  width: 100%; padding: 12px 14px; border-radius: var(--radius);
  background: var(--bg-3); border: 1px solid var(--border);
  color: var(--text); font-family: var(--font); font-size: 15px;
  transition: border-color .3s ease;
}
.field input:focus, .field textarea:focus { outline: 0; border-color: #a855f7; }
.field .err { color: #ec4899; font-size: 13px; margin-top: 5px; display: none; }
.field.invalid .err { display: block; }
.form-msg { margin-top: 10px; font-size: 14px; }
.form-msg.ok { color: #4ade80; }
.form-msg.bad { color: #ec4899; }

/* ---------- 页脚 ---------- */
.footer {
  border-top: 1px solid var(--border);
  padding: 28px 0; color: var(--text-3); font-size: 13px;
  display: flex; justify-content: space-between; flex-wrap: wrap; gap: 8px;
  transition: border-color .3s ease;
}
.footer a { color: inherit; text-decoration: none; transition: color .2s ease; }
.footer a:hover { color: var(--accent); }

/* ---------- 加载淡入 ---------- */
.fade { opacity: 0; transform: translateY(16px); animation: fadeUp .7s ease forwards; }
.fade.d1 { animation-delay: .08s; }
.fade.d2 { animation-delay: .16s; }
.fade.d3 { animation-delay: .24s; }

@keyframes fadeUp { to { opacity: 1; transform: none; } }
@keyframes logoIn { from { transform: rotate(-90deg) scale(.6); opacity: 0; } to { transform: none; opacity: 1; } }

/* ---------- 标签 ---------- */
.tag {
  display: inline-block; font-size: 12px; padding: 3px 10px;
  border-radius: 999px; background: var(--bg-3);
  border: 1px solid var(--border); color: var(--text-2);
  margin-top: 6px;
}

/* ---------- 响应式 ---------- */
@media (max-width: 1023px) {
  .grid-3 { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 767px) {
  .hero h1 { font-size: 34px; }
  .grid-3, .grid-2 { grid-template-columns: 1fr; }
  .nav-links {
    position: absolute; top: var(--nav-h); left: 0; right: 0;
    flex-direction: column; gap: 0; background: var(--bg);
    border-bottom: 1px solid var(--border);
    max-height: 0; overflow: hidden; transition: max-height .3s;
  }
  .nav-links.open { max-height: 320px; }
  .nav-links a { padding: 14px 20px; width: 100%; border-bottom: 1px solid var(--border); }
  .nav-toggle { display: inline-flex; }
  .nav-right { gap: 8px; }
  section { padding: 56px 0; }
}

/* ---------- 案例详情页 ---------- */
.case-hero { text-align: center; max-width: 720px; margin: 0 auto; }
.case-hero .section-sub { margin-top: 12px; }
.case-figure { margin: 0 0 32px; }
.case-figure img {
  width: 100%; height: auto; display: block;
  border-radius: 14px; border: 1px solid var(--border);
  box-shadow: 0 10px 30px rgba(0, 0, 0, .08);
}
.case-figure figcaption {
  margin-top: 12px; font-size: 13px; color: var(--text-2); text-align: center;
}
.case-features { list-style: none; padding: 0; margin: 0; display: grid; gap: 14px; }
.case-features li {
  display: flex; gap: 10px; align-items: flex-start;
  padding: 14px 16px; border: 1px solid var(--border); border-radius: 12px;
  background: var(--bg);
}
.case-features .dot { color: var(--accent, #4f7cff); font-weight: 700; line-height: 1.5; }
.case-split { display: grid; grid-template-columns: 1fr 1fr; gap: 40px; align-items: center; }
@media (max-width: 767px) { .case-split { grid-template-columns: 1fr; gap: 24px; } }