/* ============================================================
   费曼AI教育系统 官网样式
   品牌主色沿用飞书蓝 #3370FF（对齐 apps/web/src/styles.css）
   纯静态、无外部依赖
   ============================================================ */

:root {
  --primary: #3370FF;
  --primary-hover: #245BDB;
  --primary-active: #1C4CBF;
  --primary-soft: #EAF0FF;
  --ink: #1D2129;
  --ink-2: #4E5969;
  --ink-3: #86909C;
  --line: #E5E6EB;
  --bg: #FFFFFF;
  --bg-soft: #F7F8FA;
  --radius-s: 4px;
  --radius-m: 8px;
  --radius-l: 16px;
  --shadow-sm: 0 2px 8px rgba(29, 33, 41, .06);
  --shadow-md: 0 8px 28px rgba(29, 33, 41, .10);
  --shadow-lg: 0 20px 60px rgba(51, 112, 255, .18);
  --maxw: 1160px;
  --font: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei",
          "Helvetica Neue", Arial, "Noto Sans SC", sans-serif;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: var(--font);
  color: var(--ink);
  background: var(--bg);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

a { color: inherit; text-decoration: none; }
img, svg { display: block; max-width: 100%; }

.container { width: 100%; max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }

/* ---------- 通用按钮 ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center;
  height: 48px; padding: 0 26px;
  font-size: 16px; font-weight: 600;
  border-radius: var(--radius-m);
  transition: all .2s ease; cursor: pointer; border: 1px solid transparent;
  white-space: nowrap;
}
.btn-primary { background: var(--primary); color: #fff; box-shadow: 0 6px 18px rgba(51,112,255,.28); }
.btn-primary:hover { background: var(--primary-hover); transform: translateY(-1px); box-shadow: 0 10px 24px rgba(51,112,255,.34); }
.btn-primary:active { background: var(--primary-active); transform: translateY(0); }
.btn-ghost { background: transparent; color: var(--primary); border-color: transparent; }
.btn-ghost:hover { background: var(--primary-soft); }

/* ---------- eyebrow / 段标题 ---------- */
.eyebrow {
  display: inline-block; font-size: 13px; font-weight: 700; letter-spacing: 1px;
  color: var(--primary); background: var(--primary-soft);
  padding: 5px 12px; border-radius: 99px; margin-bottom: 16px;
}
.eyebrow-light { color: #fff; background: rgba(255,255,255,.18); }

.section { padding: 96px 0; }
.section-head { text-align: center; max-width: 720px; margin: 0 auto 56px; }
.section-head h2, .section h2 { font-size: 36px; font-weight: 800; letter-spacing: -.5px; line-height: 1.25; }
.section-sub { margin-top: 16px; font-size: 17px; color: var(--ink-2); }
.section-sub.light { color: rgba(255,255,255,.8); }
.section-soft { background: var(--bg-soft); }

/* ============ 顶部导航 ============ */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: rgba(255,255,255,.85);
  backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid var(--line);
}
.nav { display: flex; align-items: center; justify-content: space-between; height: 66px; }
.brand { display: flex; align-items: center; gap: 10px; }
.brand-mark { border-radius: 9px; box-shadow: 0 4px 12px rgba(51,112,255,.3); }
.brand-text { font-size: 19px; font-weight: 800; letter-spacing: -.3px; }
.brand-text b { color: var(--primary); }
.nav-links { display: flex; align-items: center; gap: 32px; }
.nav-links a { font-size: 15px; font-weight: 500; color: var(--ink-2); transition: color .2s; }
.nav-links a:hover { color: var(--primary); }
.nav-links .nav-cta {
  color: #fff; background: var(--primary); padding: 9px 20px;
  border-radius: var(--radius-m); font-weight: 600;
}
.nav-links .nav-cta:hover { background: var(--primary-hover); color: #fff; }

.nav-toggle { display: none; flex-direction: column; gap: 5px; background: none; border: 0; cursor: pointer; padding: 8px; }
.nav-toggle span { width: 24px; height: 2px; background: var(--ink); border-radius: 2px; transition: .3s; }
.nav-toggle[aria-expanded="true"] span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ============ Hero ============ */
.hero {
  position: relative; overflow: hidden;
  padding: 84px 0 76px;
  background:
    radial-gradient(1000px 480px at 80% -10%, rgba(51,112,255,.12), transparent 60%),
    radial-gradient(760px 400px at 0% 10%, rgba(51,112,255,.06), transparent 55%);
}
.hero-inner { display: grid; grid-template-columns: 1.05fr .95fr; gap: 56px; align-items: center; }
.hero-copy h1 { font-size: 52px; font-weight: 800; line-height: 1.15; letter-spacing: -1px; margin-bottom: 22px; }
.hero-copy .lead { font-size: 18px; color: var(--ink-2); max-width: 560px; }
.hero-copy .lead b { color: var(--ink); font-weight: 700; }
.hero-actions { display: flex; gap: 14px; margin: 32px 0 22px; flex-wrap: wrap; }
.hero-badges { display: flex; flex-wrap: wrap; gap: 18px; list-style: none; }
.hero-badges li { font-size: 14px; color: var(--ink-3); font-weight: 500; }

/* Hero 视觉 */
.hero-visual { position: relative; }
.mock-card {
  background: #fff; border: 1px solid var(--line); border-radius: var(--radius-l);
  box-shadow: var(--shadow-lg); overflow: hidden; transform: rotate(.6deg);
}
.mock-head {
  display: flex; align-items: center; gap: 8px;
  padding: 14px 18px; border-bottom: 1px solid var(--line); background: var(--bg-soft);
}
.mock-dot { width: 10px; height: 10px; border-radius: 50%; background: #E5E6EB; }
.mock-dot:nth-child(1){ background:#FF7875; } .mock-dot:nth-child(2){ background:#FFC53D; } .mock-dot:nth-child(3){ background:#95DE64; }
.mock-title { margin-left: auto; font-size: 13px; font-weight: 600; color: var(--ink-2); }
.mock-body { padding: 22px; }
.mock-row { display: flex; align-items: center; justify-content: space-between; margin-bottom: 16px; }
.tag { display: inline-block; font-size: 13px; font-weight: 600; padding: 4px 12px; border-radius: 99px; }
.tag-blue { color: var(--primary); background: var(--primary-soft); }
.mock-time { font-size: 13px; color: var(--ink-3); }
.mock-line { height: 11px; border-radius: 6px; background: linear-gradient(90deg,#EEF1F6,#F6F8FB); margin-bottom: 11px; }
.mock-line.w90{width:90%;} .mock-line.w80{width:80%;} .mock-line.w70{width:70%;}
.mock-kv { display: grid; grid-template-columns: repeat(3,1fr); gap: 12px; margin: 20px 0; }
.mock-kv div { background: var(--bg-soft); border-radius: var(--radius-m); padding: 12px; text-align: center; }
.mock-kv em { display: block; font-style: normal; font-size: 12px; color: var(--ink-3); margin-bottom: 4px; }
.mock-kv b { font-size: 18px; color: var(--primary); }
.mock-foot { display: flex; align-items: center; gap: 10px; font-size: 13px; color: var(--ink-2); border-top: 1px dashed var(--line); padding-top: 16px; }
.mock-foot b { color: var(--ink); }
.mock-avatar { width: 26px; height: 26px; border-radius: 50%; background: var(--primary); color: #fff; font-size: 12px; display: grid; place-items: center; font-weight: 600; }
.mock-check { margin-left: auto; color: #00B42A; font-weight: 700; }
.mock-float {
  position: absolute; background: #fff; border: 1px solid var(--line);
  box-shadow: var(--shadow-md); border-radius: 99px; padding: 8px 16px;
  font-size: 14px; font-weight: 600; color: var(--ink);
  animation: float 4s ease-in-out infinite;
}
.mock-float-1 { top: -18px; left: -14px; }
.mock-float-2 { bottom: 24px; right: -20px; animation-delay: 1.2s; }
@keyframes float { 0%,100%{ transform: translateY(0);} 50%{ transform: translateY(-9px);} }

/* ============ 信任条 ============ */
.strip { border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); background: var(--bg-soft); }
.strip-inner { display: grid; grid-template-columns: repeat(4,1fr); gap: 20px; padding: 30px 24px; }
.strip-item { text-align: center; }
.strip-item b { display: block; font-size: 22px; font-weight: 800; color: var(--primary); }
.strip-item span { font-size: 14px; color: var(--ink-3); }

/* ============ 栅格 ============ */
.grid { display: grid; gap: 24px; }
.grid-3 { grid-template-columns: repeat(3,1fr); }
.grid-2 { grid-template-columns: repeat(2,1fr); }

/* 功能卡 */
.feature {
  background: #fff; border: 1px solid var(--line); border-radius: var(--radius-l);
  padding: 30px 28px; transition: all .25s ease;
}
.feature:hover { border-color: rgba(51,112,255,.4); box-shadow: var(--shadow-md); transform: translateY(-4px); }
.feature-ico {
  width: 52px; height: 52px; border-radius: var(--radius-m);
  background: var(--primary-soft); display: grid; place-items: center;
  font-size: 26px; margin-bottom: 18px;
}
.feature h3 { font-size: 20px; font-weight: 700; margin-bottom: 10px; }
.feature p { font-size: 15px; color: var(--ink-2); }

/* ============ AI 亮点 ============ */
.section-ai {
  background: linear-gradient(135deg, #2B5CE6 0%, #3370FF 50%, #4E7BFF 100%);
  color: #fff;
}
.ai-inner { display: grid; grid-template-columns: 1fr 1fr; gap: 56px; align-items: center; }
.ai-copy h2 { color: #fff; }
.check-list { list-style: none; margin-top: 24px; display: grid; gap: 14px; }
.check-list li { position: relative; padding-left: 32px; font-size: 16px; color: rgba(255,255,255,.92); }
.check-list li::before {
  content: "✓"; position: absolute; left: 0; top: 0;
  width: 22px; height: 22px; border-radius: 50%;
  background: rgba(255,255,255,.2); color: #fff; font-size: 13px; font-weight: 700;
  display: grid; place-items: center;
}
.ai-pipe {
  display: flex; align-items: center; justify-content: center; flex-wrap: wrap; gap: 10px;
  background: rgba(255,255,255,.1); border: 1px solid rgba(255,255,255,.2);
  border-radius: var(--radius-l); padding: 32px 22px; backdrop-filter: blur(6px);
}
.pipe-step {
  display: flex; flex-direction: column; align-items: center; text-align: center;
  background: rgba(255,255,255,.14); border-radius: var(--radius-m); padding: 16px 14px; min-width: 96px;
}
.pipe-ico { font-size: 30px; margin-bottom: 8px; }
.pipe-step b { font-size: 15px; }
.pipe-step em { font-style: normal; font-size: 12px; color: rgba(255,255,255,.75); margin-top: 2px; }
.pipe-arrow { font-size: 22px; color: rgba(255,255,255,.7); font-weight: 700; }

/* ============ 流程 ============ */
.flow { list-style: none; display: grid; grid-template-columns: repeat(5,1fr); gap: 20px; counter-reset: step; }
.flow-item { position: relative; background: #fff; border: 1px solid var(--line); border-radius: var(--radius-l); padding: 26px 20px; }
.flow-num {
  width: 40px; height: 40px; border-radius: 50%; background: var(--primary); color: #fff;
  font-size: 18px; font-weight: 800; display: grid; place-items: center; margin-bottom: 14px;
}
.flow-item h3 { font-size: 17px; font-weight: 700; margin-bottom: 6px; }
.flow-item p { font-size: 14px; color: var(--ink-2); }

/* ============ 适用对象 ============ */
.audience-card { background: #fff; border: 1px solid var(--line); border-radius: var(--radius-l); padding: 34px 30px; }
.audience-card h3 { font-size: 21px; font-weight: 700; margin-bottom: 16px; }
.chips { display: flex; flex-wrap: wrap; gap: 10px; margin-bottom: 16px; }
.chips span { font-size: 14px; font-weight: 500; color: var(--primary); background: var(--primary-soft); padding: 6px 14px; border-radius: 99px; }
.audience-card p { font-size: 15px; color: var(--ink-2); }

/* ============ CTA ============ */
.section-cta { background: var(--bg-soft); text-align: center; }
.cta-inner { max-width: 720px; margin: 0 auto; }
.cta-inner h2 { font-size: 34px; }
.cta-inner > p { margin-top: 14px; font-size: 17px; color: var(--ink-2); }
.cta-contacts { display: flex; justify-content: center; flex-wrap: wrap; gap: 16px; margin: 30px 0 14px; }
.contact-pill {
  display: inline-flex; align-items: center; gap: 8px;
  background: #fff; border: 1px solid var(--line); border-radius: 99px;
  padding: 13px 24px; font-size: 16px; font-weight: 600; transition: all .2s;
}
.contact-pill:hover { border-color: var(--primary); color: var(--primary); box-shadow: var(--shadow-sm); }
.cta-note { font-size: 14px; color: var(--ink-3); }

/* ============ Footer ============ */
.site-footer { background: #1D2129; color: rgba(255,255,255,.75); padding: 48px 0; }
.footer-inner { display: flex; align-items: flex-start; justify-content: space-between; flex-wrap: wrap; gap: 24px; }
.footer-brand .brand-text { color: #fff; font-size: 18px; }
.footer-brand .brand-text b { color: #6E9BFF; }
.footer-brand p { font-size: 14px; margin-top: 8px; color: rgba(255,255,255,.5); }
.footer-meta { text-align: right; font-size: 14px; line-height: 1.9; }
.footer-meta a { color: rgba(255,255,255,.65); }
.footer-meta a:hover { color: #fff; text-decoration: underline; }

/* ============ 滚动进场动画 ============ */
/* 仅在 JS 生效（<html class="js">）时才隐藏待进场元素；无 JS 时全部正常显示 */
.js .reveal { opacity: 0; transform: translateY(24px); transition: opacity .6s ease, transform .6s ease; }
.js .reveal.in { opacity: 1; transform: none; }
@media (prefers-reduced-motion: reduce) {
  .reveal { opacity: 1; transform: none; transition: none; }
  .mock-float { animation: none; }
  html { scroll-behavior: auto; }
}

/* ============ 响应式 ============ */
@media (max-width: 960px) {
  .hero-inner { grid-template-columns: 1fr; gap: 48px; }
  .hero-visual { max-width: 460px; margin: 0 auto; }
  .ai-inner { grid-template-columns: 1fr; gap: 40px; }
  .grid-3 { grid-template-columns: repeat(2,1fr); }
  .flow { grid-template-columns: repeat(2,1fr); }
  .hero-copy h1 { font-size: 42px; }
}

@media (max-width: 680px) {
  .nav-links {
    position: fixed; top: 66px; left: 0; right: 0;
    flex-direction: column; align-items: stretch; gap: 0;
    background: #fff; border-bottom: 1px solid var(--line);
    padding: 8px 24px 20px; box-shadow: var(--shadow-md);
    transform: translateY(-120%); transition: transform .3s ease; visibility: hidden;
  }
  .nav-links.open { transform: translateY(0); visibility: visible; }
  .nav-links a { padding: 14px 0; border-bottom: 1px solid var(--bg-soft); font-size: 16px; }
  .nav-links .nav-cta { text-align: center; margin-top: 10px; padding: 13px; }
  .nav-toggle { display: flex; }

  .section { padding: 64px 0; }
  .section-head h2, .section h2 { font-size: 28px; }
  .hero { padding: 56px 0; }
  .hero-copy h1 { font-size: 34px; }
  .hero-copy .lead { font-size: 16px; }
  .strip-inner { grid-template-columns: repeat(2,1fr); gap: 24px 12px; }
  .grid-3, .grid-2 { grid-template-columns: 1fr; }
  .flow { grid-template-columns: 1fr; }
  .footer-inner { flex-direction: column; }
  .footer-meta { text-align: left; }
  .cta-inner h2 { font-size: 26px; }
  .btn { width: 100%; }
  .hero-actions { flex-direction: column; }
}