/* ========== 基础 ========== */
:root{
  --bg-1:#0f1122;
  --bg-2:#1a1f4a;
  --card:#13162b;
  --card-2:#0f142a;
  --txt:#e9ecf2;
  --muted:#b7bfd8;
  --brand:#5af;
  --brand-2:#3dd68c;
  --danger:#ff4d4f;
  --shadow:0 12px 30px rgba(0,0,0,.35);
  --radius:18px;
}

*{box-sizing:border-box}
html,body{height:100%}
body{
  margin:0;
  font-family:system-ui,-apple-system,Segoe UI,Roboto,Inter,Arial,sans-serif;
  color:var(--txt);
  background: radial-gradient(1200px 500px at 50% -20%, #241b49 0%, #12152b 55%, #0b0d18 100%),
              linear-gradient(160deg,var(--bg-1),var(--bg-2));
  -webkit-font-smoothing:antialiased;
  -moz-osx-font-smoothing:grayscale;
}

img{max-width:100%;display:block}

/* 容器 */
.container{
  width:min(100%, 1100px);
  padding:0 16px;
  margin-inline:auto;
}

/* 顶部导航 */
.site-header{
  position:sticky;top:0;z-index:10;
  backdrop-filter:saturate(180%) blur(10px);
  background:rgba(10,12,24,.55);
  border-bottom:1px solid rgba(255,255,255,.06);
}
.nav{
  height:60px; display:flex; align-items:center; justify-content:space-between;
}
.brand{display:flex;gap:10px;align-items:center;color:var(--txt);font-weight:800;text-decoration:none}
.brand span{opacity:.9}
.link-small{color:#fff;text-decoration:none;font-weight:700;opacity:.9}
.link-small:hover{opacity:1; text-decoration:underline}

/* Hero */
.hero{padding:24px 16px 8px}
.hero-card{
  background:linear-gradient(180deg, rgba(255,255,255,.03), rgba(255,255,255,.01));
  box-shadow:var(--shadow);
  border-radius:24px;
  padding:24px;
  border:1px solid rgba(255,255,255,.08);
}
.hero-head{ text-align:center }
.hero-logo{width:72px;height:72px;margin:0 auto 12px; border-radius:16px}
h1{
  font-size:28px; line-height:1.25; margin:6px 0 8px; font-weight:900;
  letter-spacing:.3px;
}
.sub{color:var(--muted); margin:0 auto 18px; max-width:54ch}

/* CTA 按钮（移动优先） */
.cta-stack{ display:grid; grid-template-columns:1fr; gap:10px }
.btn{
  display:flex; align-items:center; justify-content:center; gap:8px;
  height:48px; border-radius:999px; text-decoration:none; font-weight:800;
  letter-spacing:.2px; box-shadow:0 6px 18px rgba(0,0,0,.25);
  border:1px solid rgba(255,255,255,.12);
  background:#fff; color:#0b0d18;
}
.btn .ico{font-size:18px}
.btn-android{ background:linear-gradient(180deg,#66b3ff,#2f79ff); color:#fff }
.btn-ios{ background:linear-gradient(180deg,#49d58a,#1fb373); color:#0a1912 }
.btn-register{ background:#fff; color:#111; position:relative }
.btn-register::after{
  content:""; position:absolute; inset:-3px; border-radius:inherit;
  box-shadow:0 0 0 3px rgba(255,77,79,.65); pointer-events:none;
}

/* Section 标题 */
.section{ padding:28px 0 }
h2{ font-size:22px; margin:0 0 14px; font-weight:900 }

/* 特性卡片 */
.features{
  display:grid; gap:12px;
  grid-template-columns:1fr;
}
.card{
  background:var(--card);
  border:1px solid rgba(255,255,255,.06);
  border-radius:var(--radius);
  padding:16px;
  box-shadow:var(--shadow);
}
.card-head{ display:flex; align-items:center; gap:10px; margin-bottom:8px }
.card .emoji{ font-size:22px }
.card h3{ font-size:18px; margin:0 }
.card p{ margin:0; color:var(--muted) }

/* 步骤 */
.steps{ padding-left:18px; margin:0; display:grid; gap:8px }
.steps li{ line-height:1.6 }

/* FAQ */
.faq{
  background:var(--card-2);
  border:1px solid rgba(255,255,255,.06);
  border-radius:14px; padding:12px 14px;
  margin-bottom:10px;
}
.faq summary{cursor:pointer; font-weight:800}
.faq p{margin:.6rem 0 0; color:var(--muted)}

/* 页脚 */
.site-footer{ padding:28px 0 40px; color:var(--muted); text-align:center }

/* ========== 响应式 ========== */
@media (min-width:640px){
  .hero{padding:40px 16px 16px}
  .hero-card{padding:28px}
  h1{font-size:34px}
  .cta-stack{ grid-template-columns:repeat(3,minmax(0,1fr)); }
  .features{ grid-template-columns:repeat(3,minmax(0,1fr)); }
}

@media (min-width:1024px){
  .hero{padding:56px 16px 24px}
  h1{font-size:40px}
  .sub{font-size:18px}
}