/* ============================================================
   知白小助手 · 官网样式
   品牌色：#667eea → #764ba2 紫蓝渐变
   ============================================================ */

/* ---------- 设计变量 ---------- */
:root {
  --brand-from: #667eea;
  --brand-to: #764ba2;
  --brand-1: #667eea;
  --brand-1-dark: #5568d3;
  --ink: #1a1a2e;
  --ink-2: #3d3d56;
  --muted: #6b7280;
  --line: #ececf2;
  --bg-soft: #f7f8fc;
  --bg-card: #ffffff;
  --shadow-sm: 0 2px 8px rgba(30, 30, 60, 0.06);
  --shadow-md: 0 10px 30px rgba(102, 126, 234, 0.12);
  --shadow-lg: 0 24px 60px rgba(102, 126, 234, 0.18);
  --radius: 16px;
  --radius-sm: 10px;
  --maxw: 1180px;
  --gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --gradient-soft: linear-gradient(135deg, rgba(102,126,234,.12) 0%, rgba(118,75,162,.12) 100%);
}

/* ---------- 重置 ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  color: var(--ink);
  background: #ffffff;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}
img { max-width: 100%; display: block; }
a { color: inherit; text-decoration: none; }
button { font-family: inherit; cursor: pointer; }
h1, h2, h3, h4 { margin: 0; line-height: 1.25; font-weight: 700; }

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

/* 通用渐变文字 */
.grad-text {
  background: var(--gradient);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  color: transparent;
}

/* ---------- 按钮 ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  height: 50px; padding: 0 26px; border: none; border-radius: 999px;
  font-size: 16px; font-weight: 600; transition: all .2s ease; white-space: nowrap;
}
.btn-primary { background: var(--gradient); color: #fff; box-shadow: var(--shadow-md); }
.btn-primary:hover { transform: translateY(-2px); box-shadow: var(--shadow-lg); }
.btn-ghost { background: rgba(255,255,255,.9); color: var(--ink); border: 1.5px solid var(--line); }
.btn-ghost:hover { border-color: var(--brand-1); color: var(--brand-1); }
.btn-lg { height: 58px; padding: 0 34px; font-size: 17px; }

/* ---------- 导航栏 ---------- */
.nav {
  position: fixed; top: 0; left: 0; right: 0; z-index: 100;
  background: rgba(255,255,255,.85); backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid transparent; transition: all .25s ease;
}
.nav.scrolled { border-bottom-color: var(--line); box-shadow: var(--shadow-sm); }
.nav-inner { display: flex; align-items: center; justify-content: space-between; height: 68px; }
.brand { display: flex; align-items: center; gap: 10px; font-weight: 800; font-size: 19px; }
.brand img { width: 34px; height: 34px; border-radius: 8px; }
.nav-links { display: flex; align-items: center; gap: 30px; }
.nav-links a { font-size: 15px; color: var(--ink-2); font-weight: 500; transition: color .2s; }
.nav-links a:hover { color: var(--brand-1); }
.nav-cta { display: flex; align-items: center; gap: 14px; }
.nav-cta .btn { height: 42px; padding: 0 20px; font-size: 14px; }

.nav-toggle { display: none; background: none; border: none; padding: 8px; }
.nav-toggle span {
  display: block; width: 24px; height: 2px; background: var(--ink); border-radius: 2px;
  transition: .3s; position: relative;
}
.nav-toggle span + span { margin-top: 6px; }

/* ---------- Hero ---------- */
.hero {
  position: relative; padding: 150px 0 90px; overflow: hidden;
  background:
    radial-gradient(900px 500px at 85% -5%, rgba(118,75,162,.16), transparent 60%),
    radial-gradient(800px 500px at 10% 0%, rgba(102,126,234,.16), transparent 55%),
    #ffffff;
}
.hero-grid { display: grid; grid-template-columns: 1.05fr .95fr; gap: 56px; align-items: center; }
.hero-badge {
  display: inline-flex; align-items: center; gap: 8px; padding: 7px 16px;
  background: var(--gradient-soft); border: 1px solid rgba(102,126,234,.25);
  border-radius: 999px; font-size: 13px; font-weight: 600; color: var(--brand-1);
  margin-bottom: 22px;
}
.hero h1 { font-size: 52px; letter-spacing: -.5px; margin-bottom: 18px; }
.hero-sub { font-size: 19px; color: var(--muted); margin: 0 0 14px; max-width: 520px; }
.hero-desc { font-size: 15px; color: var(--ink-2); max-width: 500px; margin-bottom: 30px; }
.hero-actions { display: flex; flex-wrap: wrap; gap: 14px; margin-bottom: 26px; }
.hero-meta { display: flex; gap: 22px; font-size: 13.5px; color: var(--muted); flex-wrap: wrap; }
.hero-meta span { display: inline-flex; align-items: center; gap: 6px; }
.dot { width: 6px; height: 6px; border-radius: 50%; background: #22c55e; }

/* Hero 右侧应用视觉（CSS 模拟界面） */
.app-window {
  background: #fff; border-radius: 16px; box-shadow: var(--shadow-lg);
  overflow: hidden; border: 1px solid var(--line); transform: perspective(1200px) rotateY(-6deg) rotateX(2deg);
}
.win-bar { display: flex; align-items: center; gap: 7px; padding: 12px 16px; background: #f5f6fb; border-bottom: 1px solid var(--line); }
.win-bar i { width: 11px; height: 11px; border-radius: 50%; display: inline-block; }
.win-bar .r { background: #ff5f57; } .win-bar .y { background: #febc2e; } .win-bar .g { background: #28c840; }
.win-body { display: grid; grid-template-columns: 132px 1fr; min-height: 330px; }
.win-side { background: linear-gradient(180deg,#2b2b52,#3a3a6e); padding: 16px 12px; }
.win-side .wlogo { color:#fff; font-size:12px; font-weight:700; margin-bottom:16px; display:flex; align-items:center; gap:6px;}
.win-side .wlogo b{ display:inline-block; width:16px; height:16px; border-radius:5px; background:var(--gradient);}
.win-side .item { height: 10px; border-radius: 5px; background: rgba(255,255,255,.16); margin-bottom: 12px; }
.win-side .item.on { background: var(--gradient); }
.win-main { padding: 18px; }
.win-title { height: 12px; width: 40%; border-radius: 6px; background: var(--ink); opacity:.75; margin-bottom: 16px; }
.cards { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.cards .card { border-radius: 12px; padding: 14px; background: var(--bg-soft); border:1px solid var(--line); }
.cards .card .n { height: 10px; width: 60%; border-radius:5px; background:#cfd3e8; margin-bottom: 10px;}
.cards .card .v { height: 22px; width: 70%; border-radius:6px; background: var(--gradient); opacity:.85;}
.cards .wide { grid-column: 1 / -1; height: 64px; background: var(--gradient-soft); display:flex; align-items:center; padding: 0 16px;}
.cards .wide .v2{ height:10px; width:55%; border-radius:5px; background: rgba(102,126,234,.45);}

/* ---------- 数据条 ---------- */
.stats { padding: 40px 0; background: var(--bg-soft); border-top:1px solid var(--line); border-bottom:1px solid var(--line);}
.stats-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 24px; text-align: center; }
.stat .num { font-size: 38px; font-weight: 800; }
.stat .lbl { font-size: 14px; color: var(--muted); margin-top: 4px; }

/* ---------- 通用 section ---------- */
.section { padding: 92px 0; }
.section-soft { background: var(--bg-soft); }
.sec-head { text-align: center; max-width: 680px; margin: 0 auto 56px; }
.sec-eyebrow { font-size: 14px; font-weight: 700; color: var(--brand-1); letter-spacing: 1px; text-transform: uppercase; }
.sec-title { font-size: 38px; margin: 12px 0 14px; letter-spacing: -.3px; }
.sec-desc { font-size: 16px; color: var(--muted); }

/* ---------- 服务三阶段 ---------- */
.phases { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.phase {
  background: var(--bg-card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 30px 26px; box-shadow: var(--shadow-sm); transition: transform .25s, box-shadow .25s;
}
.phase:hover { transform: translateY(-6px); box-shadow: var(--shadow-md); }
.phase-tag {
  display: inline-block; padding: 5px 14px; border-radius: 999px; font-size: 13px; font-weight: 700;
  color: #fff; background: var(--gradient); margin-bottom: 16px;
}
.phase h3 { font-size: 21px; margin-bottom: 6px; }
.phase .phase-sub { font-size: 14px; color: var(--muted); margin-bottom: 18px; }
.phase ul { list-style: none; padding: 0; margin: 0; }
.phase li { display: flex; gap: 10px; padding: 9px 0; font-size: 14.5px; color: var(--ink-2); border-top: 1px dashed var(--line); }
.phase li:first-child { border-top: none; }
.phase li::before { content: ""; flex: none; width: 18px; height: 18px; border-radius: 50%; background: var(--gradient-soft); margin-top: 2px; position: relative; }
.phase li .ico { flex:none; width:18px; height:18px; margin-top:2px; color: var(--brand-1); }

/* ---------- 亮点特性 ---------- */
.features { display: grid; grid-template-columns: repeat(4, 1fr); gap: 22px; }
.feature {
  background: #fff; border: 1px solid var(--line); border-radius: var(--radius);
  padding: 28px 22px; transition: transform .25s, box-shadow .25s;
}
.feature:hover { transform: translateY(-5px); box-shadow: var(--shadow-md); border-color: rgba(102,126,234,.4); }
.feature .ficon {
  width: 52px; height: 52px; border-radius: 14px; display: flex; align-items: center; justify-content: center;
  background: var(--gradient-soft); color: var(--brand-1); margin-bottom: 16px; font-size: 24px;
}
.feature h3 { font-size: 18px; margin-bottom: 8px; }
.feature p { font-size: 14px; color: var(--muted); margin: 0; }

/* ---------- 平台 ---------- */
.platforms { display: flex; flex-wrap: wrap; justify-content: center; gap: 16px; }
.platform {
  display: inline-flex; align-items: center; gap: 10px; padding: 14px 26px;
  background: #fff; border: 1px solid var(--line); border-radius: 999px;
  font-weight: 600; font-size: 16px; box-shadow: var(--shadow-sm);
}
.platform .pemoji { font-size: 22px; }

/* ---------- 下载区 ---------- */
.download { padding: 96px 0; background: var(--gradient); color: #fff; position: relative; overflow: hidden; }
.download::before {
  content: ""; position: absolute; inset: 0;
  background: radial-gradient(700px 300px at 20% 10%, rgba(255,255,255,.15), transparent 60%);
}
.download .sec-eyebrow { color: rgba(255,255,255,.85); }
.download .sec-title, .download .sec-desc { color: #fff; }
.dl-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 26px; max-width: 820px; margin: 0 auto; position: relative; }
.dl-card {
  background: rgba(255,255,255,.12); backdrop-filter: blur(8px);
  border: 1px solid rgba(255,255,255,.25); border-radius: var(--radius); padding: 30px;
  transition: transform .25s, background .25s;
}
.dl-card:hover { transform: translateY(-5px); background: rgba(255,255,255,.18); }
.dl-card.recommend { border-color: rgba(255,255,255,.7); box-shadow: 0 16px 40px rgba(0,0,0,.18); }
.dl-head { display: flex; align-items: center; gap: 14px; margin-bottom: 18px; }
.dl-head .os { width: 50px; height: 50px; border-radius: 12px; background: rgba(255,255,255,.18); display:flex; align-items:center; justify-content:center; font-size: 26px; }
.dl-head h3 { font-size: 22px; }
.dl-head .ver { font-size: 13px; opacity: .85; }
.dl-meta { font-size: 13.5px; opacity: .9; margin-bottom: 8px; display:flex; gap:8px; }
.dl-meta b { font-weight: 600; }
.dl-req { font-size: 13px; opacity: .8; margin-bottom: 20px; }
.dl-card .btn { width: 100%; }
.dl-btn-white { background: #fff; color: var(--brand-1); }
.dl-btn-white:hover { transform: translateY(-2px); box-shadow: 0 12px 30px rgba(0,0,0,.2); }
.dl-card.unavailable .btn { background: rgba(255,255,255,.25); color: #fff; cursor: not-allowed; }
.dl-badge {
  display: inline-block; font-size: 11px; font-weight: 700; padding: 3px 10px; border-radius: 999px;
  background: #fff; color: var(--brand-1); margin-left: 8px; vertical-align: middle;
}

/* ---------- FAQ ---------- */
.faq-list { max-width: 800px; margin: 0 auto; }
.faq-item { border: 1px solid var(--line); border-radius: var(--radius-sm); background: #fff; margin-bottom: 14px; overflow: hidden; box-shadow: var(--shadow-sm); }
.faq-q {
  width: 100%; text-align: left; background: none; border: none; padding: 20px 24px;
  font-size: 16px; font-weight: 600; color: var(--ink); display: flex; justify-content: space-between; align-items: center; gap: 16px;
}
.faq-q .chev { flex: none; transition: transform .25s; color: var(--brand-1); font-size: 18px; }
.faq-item.open .faq-q .chev { transform: rotate(45deg); }
.faq-a { max-height: 0; overflow: hidden; transition: max-height .3s ease; }
.faq-a-inner { padding: 0 24px 20px; color: var(--muted); font-size: 15px; }

/* ---------- Footer ---------- */
.footer { background: #15152a; color: rgba(255,255,255,.7); padding: 56px 0 28px; }
.footer-grid { display: flex; justify-content: space-between; gap: 40px; flex-wrap: wrap; padding-bottom: 32px; border-bottom: 1px solid rgba(255,255,255,.12); }
.footer .brand { color: #fff; margin-bottom: 12px; }
.footer .brand img { background: #fff; }
.footer p { font-size: 14px; max-width: 360px; margin: 0; }
.footer-cols { display: flex; gap: 56px; flex-wrap: wrap; }
.footer-col h4 { color: #fff; font-size: 14px; margin-bottom: 14px; }
.footer-col a { display: block; font-size: 14px; padding: 5px 0; color: rgba(255,255,255,.65); transition: color .2s; }
.footer-col a:hover { color: #fff; }
.footer-bottom { padding-top: 22px; font-size: 13px; color: rgba(255,255,255,.5); display:flex; justify-content: space-between; flex-wrap: wrap; gap: 10px; }

/* ---------- 滚动淡入动画 ---------- */
.reveal { opacity: 0; transform: translateY(28px); transition: opacity .6s ease, transform .6s ease; }
.reveal.in { opacity: 1; transform: none; }

/* ---------- 响应式 ---------- */
@media (max-width: 980px) {
  .hero { padding: 120px 0 70px; }
  .hero-grid { grid-template-columns: 1fr; gap: 40px; }
  .hero h1 { font-size: 40px; }
  .app-window { transform: none; max-width: 520px; margin: 0 auto; }
  .phases { grid-template-columns: 1fr; }
  .features { grid-template-columns: repeat(2, 1fr); }
  .stats-grid { grid-template-columns: repeat(2, 1fr); gap: 32px 16px; }
  .dl-grid { grid-template-columns: 1fr; }
  .sec-title { font-size: 30px; }
}
@media (max-width: 680px) {
  .nav-links { display: none; }
  .nav-toggle { display: block; }
  .nav-cta .btn-text { display: none; }
  .nav-cta .btn { padding: 0 14px; }
  .hero h1 { font-size: 32px; }
  .hero-sub { font-size: 17px; }
  .features { grid-template-columns: 1fr; }
  .section { padding: 64px 0; }
  .stats-grid { grid-template-columns: 1fr 1fr; }
  .footer-grid { flex-direction: column; gap: 24px; }
}