:root {
    --c-primary: #229ED9;
    --c-primary-dark: #1a86ba;
    --c-primary-deep: #147aa8;
    --c-primary-soft: #e8f6fd;
    --c-accent: #2AABEE;
    --c-bg: #ffffff;
    --c-bg-soft: #f5fafd;
    --c-bg-softer: #eef7fc;
    --c-text: #0f1e28;
    --c-text-2: #4a6172;
    --c-text-3: #8ba3b3;
    --c-border: #dceaf2;
    --c-white: #ffffff;
    --grad: linear-gradient(135deg, #2AABEE 0%, #229ED9 55%, #1a86ba 100%);
    --grad-soft: linear-gradient(180deg, #eaf7fe 0%, #f7fbfe 100%);
    --font: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
    --sh-sm: 0 1px 2px rgba(20,80,120,.06);
    --sh-md: 0 6px 20px -6px rgba(20,80,120,.14);
    --sh-lg: 0 18px 44px -14px rgba(20,80,120,.22);
    --sh-xl: 0 30px 70px -22px rgba(20,80,120,.32);
    --r-sm: 8px;
    --r-md: 12px;
    --r-lg: 18px;
    --r-xl: 26px;
    --r-full: 999px;
  }

  *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
  html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
  body {
    font-family: var(--font);
    color: var(--c-text);
    background: var(--c-bg);
    line-height: 1.7;
    letter-spacing: .01em;
    -webkit-font-smoothing: antialiased;
    overflow-x: hidden;
  }
  a { color: inherit; text-decoration: none; }
  img, svg { display: block; max-width: 100%; }
  ul { list-style: none; }

  .container { max-width: 1160px; margin: 0 auto; padding: 0 1.5rem; }
  .center { text-align: center; }

  /* ===== Buttons ===== */
  .btn {
    display: inline-flex; align-items: center; justify-content: center; gap: .5rem;
    padding: .82rem 1.6rem; border-radius: var(--r-full);
    font-size: .95rem; font-weight: 600; font-family: var(--font);
    cursor: pointer; border: none; transition: all .22s ease; white-space: nowrap;
  }
  .btn-primary { background: var(--grad); color: #fff; box-shadow: 0 8px 22px -8px rgba(34,158,217,.7); }
  .btn-primary:hover { transform: translateY(-2px); box-shadow: 0 14px 30px -8px rgba(34,158,217,.85); }
  .btn-ghost { background: #fff; color: var(--c-primary-dark); border: 1.5px solid var(--c-border); }
  .btn-ghost:hover { border-color: var(--c-primary); color: var(--c-primary); background: var(--c-primary-soft); }
  .btn-lg { padding: 1rem 2.1rem; font-size: 1.03rem; }
  .btn-block { width: 100%; }

  /* ===== Section heading ===== */
  .sec { padding: 5.5rem 0; }
  .sec-soft { background: var(--c-bg-soft); }
  .sec-head { max-width: 680px; margin: 0 auto 3.5rem; text-align: center; }
  .sec-tag {
    display: inline-block; padding: .3rem .85rem; margin-bottom: 1rem;
    background: var(--c-primary-soft); color: var(--c-primary-dark);
    border-radius: var(--r-full); font-size: .82rem; font-weight: 600; letter-spacing: .04em;
  }
  .sec-head h2 { font-size: clamp(1.7rem, 3.6vw, 2.35rem); font-weight: 800; line-height: 1.25; letter-spacing: -.01em; }
  .sec-head p { margin-top: .9rem; font-size: 1.06rem; color: var(--c-text-2); line-height: 1.75; }

  /* ===== Navbar ===== */
  .nav {
    position: sticky; top: 0; z-index: 200;
    background: rgba(255,255,255,.86); backdrop-filter: blur(14px); -webkit-backdrop-filter: blur(14px);
    border-bottom: 1px solid transparent; transition: border-color .3s, box-shadow .3s;
  }
  .nav.scrolled { border-bottom-color: var(--c-border); box-shadow: var(--sh-sm); }
  .nav-in { max-width: 1160px; margin: 0 auto; padding: .85rem 1.5rem; display: flex; align-items: center; justify-content: space-between; gap: 1rem; }
  .logo { display: flex; align-items: center; gap: .6rem; font-weight: 800; font-size: 1.12rem; letter-spacing: -.01em; }
  .logo-mark { width: 34px; height: 34px; border-radius: 10px; background: var(--grad); display: grid; place-items: center; box-shadow: 0 6px 16px -6px rgba(34,158,217,.8); }
  .nav-links { display: flex; gap: 1.9rem; }
  .nav-links a { font-size: .93rem; font-weight: 500; color: var(--c-text-2); transition: color .2s; }
  .nav-links a:hover { color: var(--c-primary); }
  .nav-right { display: flex; align-items: center; gap: .9rem; }
  .nav-right .btn { padding: .58rem 1.3rem; font-size: .88rem; }
  .burger { display: none; background: none; border: none; cursor: pointer; padding: .4rem; }
  .burger i { display: block; width: 22px; height: 2px; background: var(--c-text); margin: 5px 0; border-radius: 2px; transition: .3s; }

  /* ===== Hero ===== */
  .hero { position: relative; padding: 4.5rem 0 5.5rem; background: var(--grad-soft); overflow: hidden; }
  .hero::before {
    content: ""; position: absolute; top: -180px; right: -140px; width: 520px; height: 520px;
    background: radial-gradient(circle, rgba(42,171,238,.28) 0%, rgba(42,171,238,0) 68%); border-radius: 50%;
  }
  .hero::after {
    content: ""; position: absolute; bottom: -220px; left: -160px; width: 460px; height: 460px;
    background: radial-gradient(circle, rgba(34,158,217,.18) 0%, rgba(34,158,217,0) 70%); border-radius: 50%;
  }
  .hero-grid { position: relative; display: grid; grid-template-columns: 1.05fr .95fr; gap: 3.5rem; align-items: center; }
  .hero-badge {
    display: inline-flex; align-items: center; gap: .5rem; padding: .35rem .95rem; margin-bottom: 1.4rem;
    background: #fff; border: 1px solid var(--c-border); border-radius: var(--r-full);
    font-size: .82rem; font-weight: 600; color: var(--c-primary-dark); box-shadow: var(--sh-sm);
  }
  .dot { width: 8px; height: 8px; border-radius: 50%; background: #22c55e; box-shadow: 0 0 0 4px rgba(34,197,94,.18); animation: pulse 1.8s infinite; }
  @keyframes pulse { 0%,100% { opacity: 1; } 50% { opacity: .35; } }
  .hero h1 { font-size: clamp(2.1rem, 5vw, 3.35rem); font-weight: 800; line-height: 1.15; letter-spacing: -.02em; }
  .hero h1 em { font-style: normal; color: var(--c-primary); position: relative; }
  .hero h1 em::after { content: ""; position: absolute; left: 0; right: 0; bottom: .06em; height: .28em; background: rgba(42,171,238,.22); border-radius: 4px; z-index: -1; }
  .hero-sub { margin-top: 1.4rem; font-size: 1.1rem; color: var(--c-text-2); max-width: 520px; line-height: 1.8; }
  .hero-cta { margin-top: 2.2rem; display: flex; gap: .9rem; flex-wrap: wrap; }
  .hero-stats { margin-top: 2.6rem; display: flex; gap: 2.4rem; flex-wrap: wrap; }
  .stat b { display: block; font-size: 1.65rem; font-weight: 800; color: var(--c-text); letter-spacing: -.02em; }
  .stat span { font-size: .84rem; color: var(--c-text-3); }

  /* 手机 mock 视觉 */
  .phone {
    width: 300px; margin: 0 auto; background: #0d1b24; border-radius: 34px; padding: 12px;
    box-shadow: var(--sh-xl); position: relative;
  }
  .phone::after { content: ""; position: absolute; top: 20px; left: 50%; transform: translateX(-50%); width: 82px; height: 6px; background: #1e3441; border-radius: 4px; }
  .phone-screen { background: #f0f6fa; border-radius: 24px; overflow: hidden; }
  .ph-top { background: var(--grad); padding: 2.1rem 1rem .9rem; color: #fff; }
  .ph-top .t1 { font-size: .74rem; opacity: .85; }
  .ph-top .t2 { font-size: 1rem; font-weight: 700; }
  .chat { padding: 1rem; display: flex; flex-direction: column; gap: .65rem; }
  .bubble { max-width: 82%; padding: .6rem .85rem; border-radius: 14px; font-size: .8rem; line-height: 1.5; }
  .bubble.in { background: #fff; color: var(--c-text); border-bottom-left-radius: 4px; box-shadow: var(--sh-sm); align-self: flex-start; }
  .bubble.out { background: var(--c-accent); color: #fff; border-bottom-right-radius: 4px; align-self: flex-end; }
  .cred { background: #fff; border: 1px dashed var(--c-primary); border-radius: 12px; padding: .7rem .85rem; font-size: .76rem; color: var(--c-text-2); align-self: flex-start; width: 88%; }
  .cred .row { display: flex; justify-content: space-between; padding: .18rem 0; }
  .cred .row b { color: var(--c-text); font-weight: 600; }
  .cred .tag { display: inline-block; margin-top: .4rem; background: #e7f9ee; color: #16a34a; font-size: .68rem; font-weight: 700; padding: .16rem .5rem; border-radius: 6px; }

  /* ===== Trust bar ===== */
  .trust { border-top: 1px solid var(--c-border); border-bottom: 1px solid var(--c-border); background: #fff; }
  .trust-in { max-width: 1160px; margin: 0 auto; padding: 1.3rem 1.5rem; display: flex; flex-wrap: wrap; gap: 1.2rem 2.6rem; justify-content: center; align-items: center; }
  .trust-item { display: flex; align-items: center; gap: .55rem; font-size: .9rem; font-weight: 500; color: var(--c-text-2); }
  .trust-item svg { width: 20px; height: 20px; flex-shrink: 0; }

  /* ===== Features ===== */
  .grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.5rem; }
  .feature {
    background: #fff; border: 1px solid var(--c-border); border-radius: var(--r-lg); padding: 1.9rem;
    transition: transform .28s cubic-bezier(.4,0,.2,1), box-shadow .28s, border-color .28s;
  }
  .feature:hover { transform: translateY(-5px); box-shadow: var(--sh-lg); border-color: #bfe3f5; }
  .f-ico { width: 50px; height: 50px; border-radius: 14px; background: var(--c-primary-soft); display: grid; place-items: center; margin-bottom: 1.2rem; }
  .f-ico svg { width: 26px; height: 26px; }
  .feature h3 { font-size: 1.1rem; font-weight: 700; margin-bottom: .55rem; }
  .feature p { font-size: .93rem; color: var(--c-text-2); line-height: 1.7; }

  /* ===== Pricing ===== */
  .plans { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.6rem; align-items: stretch; }
  .plan { position: relative; background: #fff; border: 1.5px solid var(--c-border); border-radius: var(--r-xl); padding: 2.1rem; display: flex; flex-direction: column; transition: transform .28s, box-shadow .28s; }
  .plan:hover { transform: translateY(-6px); box-shadow: var(--sh-lg); }
  .plan.hot { border-color: var(--c-primary); box-shadow: var(--sh-lg); }
  .plan-badge { position: absolute; top: -13px; left: 50%; transform: translateX(-50%); background: var(--grad); color: #fff; font-size: .74rem; font-weight: 700; padding: .28rem .9rem; border-radius: var(--r-full); white-space: nowrap; }
  .plan h3 { font-size: 1.22rem; font-weight: 750; }
  .plan .desc { font-size: .86rem; color: var(--c-text-3); margin-top: .3rem; min-height: 2.6em; }
  .price { margin: 1.3rem 0; display: flex; align-items: baseline; gap: .35rem; }
  .price .cur { font-size: 1.1rem; font-weight: 700; color: var(--c-primary-dark); }
  .price .num { font-size: 2.6rem; font-weight: 800; letter-spacing: -.03em; color: var(--c-text); }
  .price .unit { font-size: .85rem; color: var(--c-text-3); }
  .plan ul { margin: 0 0 1.6rem; display: flex; flex-direction: column; gap: .72rem; }
  .plan li { display: flex; gap: .6rem; font-size: .9rem; color: var(--c-text-2); line-height: 1.5; }
  .plan li svg { width: 18px; height: 18px; flex-shrink: 0; margin-top: .18rem; }
  .plan .btn { margin-top: auto; }

  /* ===== Steps ===== */
  .steps { display: grid; grid-template-columns: repeat(4, 1fr); gap: 1.5rem; }
  .step { text-align: center; position: relative; }
  .step-n {
    width: 54px; height: 54px; margin: 0 auto 1.1rem; border-radius: 50%; background: #fff;
    border: 2px solid var(--c-primary); color: var(--c-primary-dark); display: grid; place-items: center;
    font-weight: 800; font-size: 1.15rem; position: relative; z-index: 2;
  }
  .step:not(:last-child)::after { content: ""; position: absolute; top: 27px; left: calc(50% + 34px); right: calc(-50% + 34px); height: 2px; background: repeating-linear-gradient(90deg, var(--c-border) 0 8px, transparent 8px 16px); }
  .step h3 { font-size: 1.02rem; font-weight: 700; margin-bottom: .4rem; }
  .step p { font-size: .88rem; color: var(--c-text-2); }

  /* ===== FAQ ===== */
  .faq { max-width: 800px; margin: 0 auto; display: flex; flex-direction: column; gap: .85rem; }
  .qa { background: #fff; border: 1px solid var(--c-border); border-radius: var(--r-md); overflow: hidden; transition: border-color .25s, box-shadow .25s; }
  .qa[open] { border-color: #bfe3f5; box-shadow: var(--sh-md); }
  .qa summary {
    cursor: pointer; list-style: none; padding: 1.15rem 1.35rem; font-weight: 600; font-size: 1rem;
    display: flex; justify-content: space-between; align-items: center; gap: 1rem;
  }
  .qa summary::-webkit-details-marker { display: none; }
  .qa summary .chev { width: 20px; height: 20px; flex-shrink: 0; transition: transform .28s; }
  .qa[open] summary .chev { transform: rotate(180deg); }
  .qa .ans { padding: 0 1.35rem 1.2rem; font-size: .94rem; color: var(--c-text-2); line-height: 1.75; }

  /* ===== Reviews ===== */
  .reviews { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.5rem; }
  .review { background: #fff; border: 1px solid var(--c-border); border-radius: var(--r-lg); padding: 1.7rem; }
  .stars { color: #f5a623; font-size: .95rem; letter-spacing: .12em; margin-bottom: .8rem; }
  .review p { font-size: .93rem; color: var(--c-text-2); line-height: 1.75; }
  .review .who { margin-top: 1.2rem; display: flex; align-items: center; gap: .7rem; }
  .avatar { width: 38px; height: 38px; border-radius: 50%; background: var(--grad); color: #fff; display: grid; place-items: center; font-weight: 700; font-size: .9rem; }
  .who b { font-size: .9rem; display: block; }
  .who span { font-size: .78rem; color: var(--c-text-3); }

  /* ===== CTA band ===== */
  .cta-band { background: var(--grad); border-radius: var(--r-xl); padding: 3.2rem 2rem; text-align: center; position: relative; overflow: hidden; }
  .cta-band::before { content: ""; position: absolute; inset: 0; background: radial-gradient(circle at 20% 20%, rgba(255,255,255,.18), transparent 45%); }
  .cta-band h2 { position: relative; color: #fff; font-size: clamp(1.6rem, 3.4vw, 2.2rem); font-weight: 800; letter-spacing: -.01em; }
  .cta-band p { position: relative; color: rgba(255,255,255,.9); margin: .9rem auto 1.9rem; max-width: 520px; font-size: 1.02rem; }
  .cta-band .btn-white { position: relative; background: #fff; color: var(--c-primary-dark); }
  .cta-band .btn-white:hover { transform: translateY(-2px); box-shadow: 0 14px 32px -10px rgba(0,0,0,.4); }

  /* ===== Footer ===== */
  .footer { background: #0b1a22; color: #9fb6c4; padding: 3.6rem 0 1.8rem; }
  .foot-grid { display: grid; grid-template-columns: 1.8fr 1fr 1fr 1fr; gap: 2.6rem; padding-bottom: 2.4rem; }
  .foot-brand .logo { color: #fff; margin-bottom: 1rem; }
  .foot-brand p { font-size: .87rem; line-height: 1.75; max-width: 300px; color: #7f97a6; }
  .foot-col h4 { color: #fff; font-size: .8rem; font-weight: 700; text-transform: uppercase; letter-spacing: .07em; margin-bottom: 1rem; }
  .foot-col li { margin-bottom: .62rem; }
  .foot-col a { font-size: .87rem; color: #9fb6c4; transition: color .2s; }
  .foot-col a:hover { color: #fff; }
  .foot-bottom { border-top: 1px solid rgba(255,255,255,.08); padding-top: 1.6rem; display: flex; justify-content: space-between; gap: 1rem; flex-wrap: wrap; font-size: .8rem; color: #6c8494; }
  .foot-note { font-size: .78rem; color: #5f7686; margin-top: 1rem; line-height: 1.7; max-width: 780px; }

  /* ===== Reveal 动画 ===== */
  .reveal { opacity: 0; transform: translateY(26px); transition: opacity .7s ease, transform .7s cubic-bezier(.4,0,.2,1); }
  .reveal.in { opacity: 1; transform: none; }

  /* ===== Sticky 移动端购买条 ===== */
  .mobile-buy { display: none; position: fixed; bottom: 0; left: 0; right: 0; z-index: 300; background: rgba(255,255,255,.96); backdrop-filter: blur(10px); border-top: 1px solid var(--c-border); padding: .7rem 1rem; box-shadow: 0 -6px 20px -10px rgba(20,80,120,.25); }
  .mobile-buy .btn { width: 100%; }

  /* ===== Responsive ===== */
  @media (max-width: 980px) {
    .hero-grid { grid-template-columns: 1fr; gap: 3rem; text-align: center; }
    .hero-sub { margin-left: auto; margin-right: auto; }
    .hero-cta, .hero-stats { justify-content: center; }
    .grid-3, .plans, .reviews { grid-template-columns: 1fr 1fr; }
    .steps { grid-template-columns: 1fr 1fr; gap: 2.2rem 1.5rem; }
    .step:nth-child(2)::after { display: none; }
    .foot-grid { grid-template-columns: 1fr 1fr; gap: 2rem; }
  }
  @media (max-width: 720px) {
    .nav-links, .nav-right .btn-ghost { display: none; }
    .burger { display: block; }
    .nav-links.open { display: flex; flex-direction: column; gap: 1.1rem; position: absolute; top: 100%; left: 0; right: 0; background: #fff; padding: 1.4rem 1.5rem; border-bottom: 1px solid var(--c-border); box-shadow: var(--sh-md); }
    .sec { padding: 4rem 0; }
    .grid-3, .plans, .reviews { grid-template-columns: 1fr; }
    .steps { grid-template-columns: 1fr; }
    .step::after { display: none !important; }
    .foot-grid { grid-template-columns: 1fr; }
    .foot-bottom { flex-direction: column; text-align: center; }
    .mobile-buy { display: block; }
    .footer { padding-bottom: 5rem; }
  }