/* Sprint 20 — FlightFlow 官方网站样式 (Apple 风格 · 航空科技感)
   Brand color aligned with iOS AppTheme.swift: rgb(0.071, 0.22, 0.373)
   ≈ #123959 (was #12406F, off by a touch). */
:root{
  --navy:#123959;
  --navy-2:#0B2A4B;
  --navy-3:#1F5C95;
  --cyan:#5DD3FF;
  --paper:#F2F6FA;
  --paper-2:#E6EDF4;
  --ink:#0E1A2B;
  --ink-2:#3B4A5E;
  --line:#D7E0EB;
  --white:#fff;
  --shadow:0 12px 30px -16px rgba(18,57,89,.30);
  --radius:18px;
  --radius-sm:10px;
  --maxw:1180px;
}

*{box-sizing:border-box}
html,body{margin:0;padding:0}
html{scroll-behavior:smooth}
body{
  font-family:"Inter","Noto Sans SC",-apple-system,BlinkMacSystemFont,"Helvetica Neue",Arial,"PingFang SC","Hiragino Sans GB","Microsoft YaHei",sans-serif;
  color:var(--ink);
  background:var(--paper);
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
  line-height:1.55;
}
img,svg{display:block;max-width:100%}
a{color:inherit;text-decoration:none}
h1,h2,h3{color:var(--navy-2);letter-spacing:-.01em;line-height:1.15;margin:0 0 .6em}
h1{font-size:clamp(2.4rem,5vw,3.8rem);font-weight:700}
h2{font-size:clamp(1.6rem,3.2vw,2.4rem);font-weight:700}
h3{font-size:1.1rem;font-weight:600}
p{margin:0 0 1em;color:var(--ink-2)}

.container{max-width:var(--maxw);margin:0 auto;padding:0 24px}
.eyebrow{
  display:inline-block;
  font-size:.78rem;font-weight:600;letter-spacing:.14em;text-transform:uppercase;
  color:var(--navy-3);
  background:rgba(93,211,255,.16);
  border:1px solid rgba(93,211,255,.35);
  padding:.3em .8em;border-radius:999px;
}

/* ===== Topbar ===== */
.topbar{
  position:sticky;top:0;z-index:50;
  background:rgba(255,255,255,.85);
  backdrop-filter:saturate(1.4) blur(14px);
  -webkit-backdrop-filter:saturate(1.4) blur(14px);
  border-bottom:1px solid var(--line);
}
.topbar .container{
  display:flex;align-items:center;justify-content:space-between;
  height:64px;
  max-width:var(--maxw);
  margin:0 auto;
  padding-left:24px;
  padding-right:24px;
}
.brand{display:flex;align-items:center;gap:10px}
.brand-mark{display:inline-grid;place-items:center;width:36px;height:36px;border-radius:10px;background:var(--navy)}
.brand-name{font-weight:700;color:var(--navy-2);letter-spacing:.02em}
.nav{display:flex;align-items:center;gap:22px}
.nav a{color:var(--ink-2);font-size:.95rem}
.nav a:hover{color:var(--navy)}
/* Sprint 21 hotfix — topbar Download button is `.nav a.btn-primary`;
   `.nav a` (selector 0,1,1) outranks `.btn-primary` (0,1,0) so the
   primary white-on-navy look is lost. Re-assert with matching
   specificity. */
.nav a.btn-primary,
.nav a.btn-primary:hover{color:#fff;background:var(--navy)}
.nav a.btn-primary:hover{background:var(--navy-2)}
.nav-sep{
  color:var(--line);font-size:.9rem;user-select:none;
}

/* Sprint 21 — language toggle (EN / 中文) */
.lang-toggle{
  background:transparent;color:var(--navy);
  border:1px solid var(--line);border-radius:999px;
  padding:.35em .85em;font-size:.85rem;font-weight:600;
  cursor:pointer;line-height:1;min-width:42px;
  transition:border-color .15s ease,color .15s ease,background .15s ease;
}
.lang-toggle:hover{background:#fff;border-color:var(--navy);color:var(--navy-2)}
.lang-toggle:focus-visible{outline:2px solid var(--cyan);outline-offset:2px}
.btn{
  display:inline-flex;align-items:center;gap:8px;
  padding:.65em 1.1em;border-radius:999px;font-weight:600;font-size:.95rem;
  transition:transform .15s ease,box-shadow .15s ease,background .15s ease;
  cursor:pointer;border:0;
}
.btn-sm{padding:.4em .8em;font-size:.85rem}
.btn-lg{padding:.9em 1.4em;font-size:1rem}
.btn-primary{background:var(--navy);color:#fff;box-shadow:0 10px 20px -10px rgba(18,57,89,.5)}
.btn-primary:hover{background:var(--navy-2);transform:translateY(-1px)}
.btn-ghost{background:transparent;color:var(--navy);border:1px solid var(--line)}
.btn-ghost:hover{background:#fff;border-color:var(--navy)}

/* ===== Hero ===== */
.hero{
  position:relative;overflow:hidden;
  background:
    radial-gradient(1200px 600px at 90% -10%, rgba(93,211,255,.18), transparent 60%),
    radial-gradient(900px 500px at -10% 30%, rgba(18,57,89,.12), transparent 60%),
    linear-gradient(180deg, var(--paper) 0%, #fff 100%);
}
.hero-grid{
  display:grid;grid-template-columns:1.05fr .95fr;gap:60px;align-items:center;
  padding:80px 0 100px;
}
.hero-copy,
.hero-visual{padding-left:24px;padding-right:24px}
.hero-copy > *{margin-left:0}
.hero-copy h1 em{font-style:normal;color:var(--navy-3)}
.hero-tagline{
  display:block;font-size:1rem;font-weight:500;letter-spacing:.06em;
  text-transform:uppercase;color:var(--navy-3);margin-bottom:14px;
}
.lead{font-size:1.1rem;color:var(--ink-2);max-width:540px;margin:18px 0 28px}
.cta-row{display:flex;flex-wrap:wrap;gap:12px;margin-bottom:36px}
.hero-meta{list-style:none;padding:0;margin:0;display:flex;gap:36px;flex-wrap:wrap}
.hero-meta li{display:flex;flex-direction:column}
.hero-meta strong{font-size:1.4rem;color:var(--navy-2);font-weight:700}
.hero-meta span{font-size:.85rem;color:var(--ink-2)}

/* Hero visual: phone frames */
.hero-visual{position:relative;height:560px;display:grid;place-items:center}
.hero-visual .phone-stack{display:grid;grid-template-columns:repeat(2,1fr);gap:24px;max-width:560px;margin:0 auto}
.hero-visual .phone-frame{
  width:240px;height:480px;border-radius:36px;
  background:linear-gradient(180deg,#0B2A4B 0%, #061629 100%);
  padding:10px;color:#fff;position:relative;
  box-shadow:0 30px 60px -28px rgba(11,42,75,.5);
}
.hero-visual .phone-frame img{width:100%;height:100%;border-radius:28px;object-fit:cover}

/* ===== Section ===== */
.section{padding:96px 0}
.section-alt{background:#fff;border-top:1px solid var(--line);border-bottom:1px solid var(--line)}
.section-dark{
  background:linear-gradient(180deg, var(--navy) 0%, var(--navy-2) 100%);
  color:#E2ECF5;
}
.section-dark h2{color:#fff}
.section-dark p{color:rgba(226,236,245,.85)}
.section-cta{
  background:radial-gradient(800px 400px at 50% 0%, rgba(93,211,255,.25), transparent 60%), var(--paper);
  text-align:center;
}
.section-head{text-align:center;max-width:720px;margin:0 auto 56px}
.section-head p{font-size:1.05rem}

/* ===== Features ===== */
.feature-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:20px}
.feature{
  background:#fff;border:1px solid var(--line);border-radius:var(--radius);
  padding:28px;box-shadow:var(--shadow);
  transition:transform .2s ease, box-shadow .2s ease;
}
.feature:hover{transform:translateY(-3px);box-shadow:0 18px 40px -18px rgba(18,57,89,.35)}
.feature-icon{
  width:48px;height:48px;border-radius:14px;
  background:linear-gradient(135deg,var(--c1,#5DD3FF),var(--c2,#123959));
  color:#fff;display:grid;place-items:center;margin-bottom:16px;
}
.feature h3{margin-bottom:6px;color:var(--navy-2)}

/* ===== Workflow ===== */
.workflow{list-style:none;padding:0;margin:0;display:grid;grid-template-columns:repeat(4,1fr);gap:20px}
.workflow li{
  background:#fff;border:1px solid var(--line);border-radius:var(--radius);
  padding:24px;position:relative;
}
.wf-num{
  font-size:.85rem;font-weight:700;color:var(--cyan);
  background:var(--navy);display:inline-block;padding:.3em .7em;border-radius:999px;margin-bottom:14px;
  letter-spacing:.08em;
}
.wf-body h3{font-size:1.1rem;margin-bottom:6px}

/* ===== Screens ===== */
.screens{display:grid;grid-template-columns:repeat(3,1fr);gap:24px;align-items:end}
.screen{margin:0;text-align:center}
.screen-frame{
  width:240px;height:480px;border-radius:36px;
  background:linear-gradient(180deg,#0B2A4B 0%, #061629 100%);
  padding:0;color:#fff;position:relative;
  box-shadow:0 30px 60px -28px rgba(11,42,75,.5);
  margin:0 auto;overflow:hidden;
}
.screen-frame img{width:100%;height:100%;display:block;border-radius:36px}
.screen-frame figcaption,
.screen figcaption{
  margin-top:14px;font-size:.92rem;color:var(--ink-2);
}
.screen-frame-note{
  position:absolute;bottom:6px;left:50%;transform:translateX(-50%);
  font-size:.6rem;letter-spacing:.1em;text-transform:uppercase;
  color:rgba(255,255,255,.55);background:rgba(0,0,0,.4);padding:2px 8px;border-radius:999px;
}

/* ===== Highlights ===== */
.highlights{display:grid;grid-template-columns:1fr 1.2fr;gap:60px;align-items:center}
.highlights h2{margin-bottom:10px}
.highlights ul{list-style:none;padding:0;margin:0;display:grid;gap:18px}
.highlights li{
  padding:18px 20px;border-radius:14px;
  background:rgba(255,255,255,.06);
  border:1px solid rgba(255,255,255,.1);
}
.highlights b{display:block;color:#fff;margin-bottom:4px;font-size:1rem}
.highlights span{color:rgba(226,236,245,.85);font-size:.92rem}

/* ===== FAQ ===== */
.faq{max-width:760px;margin:0 auto;display:flex;flex-direction:column;gap:12px}
.faq details{
  background:#fff;border:1px solid var(--line);border-radius:14px;padding:18px 22px;
  transition:box-shadow .2s ease;
}
.faq details[open]{box-shadow:var(--shadow);border-color:transparent}
.faq summary{
  cursor:pointer;font-weight:600;color:var(--navy-2);
  list-style:none;display:flex;justify-content:space-between;align-items:center;
}
.faq summary::-webkit-details-marker{display:none}
.faq summary::after{
  content:"+";font-size:1.4rem;color:var(--navy-3);transition:transform .2s ease;
}
.faq details[open] summary::after{transform:rotate(45deg)}
.faq p{margin:12px 0 0;color:var(--ink-2)}

/* ===== CTA ===== */
.cta{padding:20px 0}
.cta h2{margin-bottom:10px}

/* ===== Footer (Sprint 20: 4-column grid) ===== */
.footer{
  background:#fff;border-top:1px solid var(--line);padding:48px 0 24px;color:var(--ink-2);
}
.footer-grid{
  display:grid;grid-template-columns:1.5fr repeat(3, 1fr);gap:40px;margin-bottom:32px;
}
.footer-brand .brand{display:flex;align-items:center;gap:10px;margin-bottom:12px}
.footer-brand .brand-mark{background:var(--navy)}
.footer-brand p{margin:8px 0 0;color:var(--ink-2);font-size:.92rem;max-width:280px}
.footer-col h4{
  font-size:.78rem;font-weight:700;color:var(--navy-3);
  text-transform:uppercase;letter-spacing:.12em;
  margin:0 0 14px;
}
.footer-col ul{list-style:none;padding:0;margin:0;display:grid;gap:10px}
.footer-col a{font-size:.92rem}
.footer-col a:hover{color:var(--navy)}
.footer-bottom{
  display:flex;justify-content:space-between;align-items:center;
  padding-top:24px;border-top:1px solid var(--line);
  font-size:.85rem;flex-wrap:wrap;gap:10px;
}
.footer-bottom .copy{color:var(--ink-2)}
.footer-bottom .legal-links{display:flex;gap:18px}

/* ===== Legal pages (privacy / terms / account-deletion / support) ===== */
.legal-page{padding:80px 0 96px;background:#fff}
.legal-page .container{max-width:820px}
.legal-page h1{
  font-size:clamp(2rem,4.2vw,2.8rem);margin-bottom:8px;
}
.legal-page .lead-sub{
  color:var(--ink-2);font-size:1rem;margin-bottom:32px;
  border-bottom:1px solid var(--line);padding-bottom:20px;
}
.legal-page h2{
  font-size:1.35rem;margin-top:36px;margin-bottom:14px;color:var(--navy-2);
  border-left:3px solid var(--cyan);padding-left:12px;
}
.legal-page h3{font-size:1.05rem;margin-top:20px;color:var(--navy-3)}
.legal-page p{font-size:.96rem;color:var(--ink-2);margin-bottom:12px}
.legal-page ul, .legal-page ol{padding-left:22px;color:var(--ink-2);font-size:.96rem;margin-bottom:14px}
.legal-page li{margin-bottom:6px}
.legal-page code{
  font-family:"SF Mono","JetBrains Mono",Menlo,monospace;
  font-size:.85rem;background:var(--paper);padding:1px 6px;border-radius:4px;color:var(--navy-2);
}
.legal-callout{
  background:linear-gradient(180deg, rgba(93,211,255,.08), rgba(18,57,89,.05));
  border:1px solid rgba(93,211,255,.3);
  border-radius:14px;padding:20px 24px;margin:24px 0;
}
.legal-callout h3{margin-top:0;color:var(--navy-2)}
.legal-callout.warning{
  background:linear-gradient(180deg, rgba(248,113,113,.08), rgba(154,46,46,.05));
  border-color:rgba(248,113,113,.35);
}
.legal-callout.warning h3{color:#7A1414}
.legal-page .back-link{
  display:inline-flex;align-items:center;gap:6px;color:var(--navy);
  font-weight:600;margin-bottom:24px;
}
.legal-page .back-link:hover{color:var(--navy-2)}
.legal-meta{
  color:var(--ink-2);font-size:.85rem;margin-top:36px;
  border-top:1px solid var(--line);padding-top:18px;
}

/* ===== Support page ===== */
.support-grid{display:grid;grid-template-columns:1.2fr .8fr;gap:48px;align-items:start}
.support-card{
  background:#fff;border:1px solid var(--line);border-radius:var(--radius);
  padding:28px;box-shadow:var(--shadow);
}
.support-card h3{margin-top:0;color:var(--navy-2)}
.support-channel{
  display:flex;align-items:center;gap:14px;padding:14px 0;
  border-bottom:1px dashed var(--line);
}
.support-channel:last-child{border-bottom:0}
.support-channel-icon{
  width:40px;height:40px;border-radius:10px;
  background:linear-gradient(135deg,var(--cyan),var(--navy));
  color:#fff;display:grid;place-items:center;flex-shrink:0;
}
.support-channel b{display:block;color:var(--navy-2);font-weight:600;margin-bottom:2px}
.support-channel span{color:var(--ink-2);font-size:.88rem}
.support-channel a{color:var(--navy);font-weight:600}

/* ===== Responsive ===== */
@media (max-width:980px){
  .hero-grid{grid-template-columns:1fr;gap:40px;padding:60px 24px}
  .hero-visual{height:auto;max-width:560px;margin:0 auto}
  .feature-grid{grid-template-columns:repeat(2,1fr)}
  .workflow{grid-template-columns:repeat(2,1fr)}
  .screens{grid-template-columns:repeat(2,1fr);gap:36px}
  .highlights{grid-template-columns:1fr;gap:36px}
  .nav a:not(.btn){display:none}
  /* Sprint 21 hotfix — keep legal links visible on mobile so App Store
     reviewers / users can always reach Privacy / Terms / Account Deletion. */
  .nav a.nav-legal{display:inline-block;font-size:.78rem;color:var(--navy);font-weight:600}
  .nav .nav-sep{display:none}
  .footer-grid{grid-template-columns:1fr 1fr;gap:32px}
  .support-grid{grid-template-columns:1fr;gap:32px}
}
@media (max-width:560px){
  .feature-grid{grid-template-columns:1fr}
  .workflow{grid-template-columns:1fr}
  .hero-meta{gap:18px}
  .screens{grid-template-columns:1fr}
  .footer-grid{grid-template-columns:1fr}
}