:root {
  --blue: #2563eb;
  --blue-d: #1d4ed8;
  --bg: #f6f7f9;
  --surface: #ffffff;
  --text: #1f2328;
  --muted: #5b6675;
  --border: #e3e6ea;
  --accent-soft: #eaf1ff;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Microsoft YaHei", sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
}
a { color: var(--blue); text-decoration: none; }
a:hover { text-decoration: underline; }

/* nav */
.nav {
  display: flex; align-items: center; justify-content: space-between;
  padding: 16px 32px; background: var(--surface);
  border-bottom: 1px solid var(--border); position: sticky; top: 0; z-index: 10;
}
.brand { font-weight: 700; font-size: 18px; display: flex; align-items: center; gap: 8px; }
.brand .logo { color: var(--blue); font-size: 20px; }
.nav nav a { margin-left: 22px; color: var(--muted); font-size: 14px; }
.nav nav a:hover { color: var(--blue); text-decoration: none; }

/* hero */
.hero {
  text-align: center; padding: 72px 24px 56px;
  background: linear-gradient(180deg, #fff 0%, var(--bg) 100%);
}
.hero h1 { font-size: 38px; margin: 0 0 14px; line-height: 1.25; }
.hero .sub { font-size: 17px; color: var(--muted); max-width: 620px; margin: 0 auto 26px; }
.cta {
  display: inline-block; background: var(--blue); color: #fff;
  padding: 12px 26px; border-radius: 8px; font-weight: 600;
}
.cta:hover { background: var(--blue-d); text-decoration: none; }

/* features */
.features { max-width: 980px; margin: 0 auto; padding: 40px 24px; }
.features h2, .pricing h2 { text-align: center; font-size: 28px; margin-bottom: 28px; }
.grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 18px; }
.card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: 12px; padding: 22px;
}
.card .ic { font-size: 24px; color: var(--blue); margin-bottom: 8px; }
.card h3 { margin: 0 0 6px; font-size: 16px; }
.card p { margin: 0; font-size: 14px; color: var(--muted); }

/* pricing */
.pricing { padding: 40px 24px 64px; }
.plan {
  max-width: 380px; margin: 0 auto; background: var(--surface);
  border: 1px solid var(--border); border-radius: 16px; padding: 32px;
  text-align: center; box-shadow: 0 6px 24px rgba(37,99,235,0.08);
}
.plan h3 { margin: 0 0 6px; font-size: 20px; }
.plan .price { font-size: 44px; font-weight: 800; color: var(--blue); }
.plan .price .per { font-size: 16px; font-weight: 500; color: var(--muted); }
.plan-tag { color: var(--muted); font-size: 13px; margin: 4px 0 18px; }
.plan ul { list-style: none; padding: 0; margin: 0 0 22px; text-align: left; }
.plan ul li { padding: 7px 0 7px 26px; position: relative; font-size: 14px; }
.plan ul li::before { content: "✓"; color: var(--blue); position: absolute; left: 0; font-weight: 700; }
.buy {
  width: 100%; background: var(--blue); color: #fff; border: none;
  padding: 13px 0; border-radius: 8px; font-size: 16px; font-weight: 600; cursor: pointer;
}
.buy:hover { background: var(--blue-d); }
.plan .note { font-size: 12px; color: var(--muted); margin: 12px 0 0; }

/* footer */
.footer {
  background: var(--surface); border-top: 1px solid var(--border);
  text-align: center; padding: 28px 24px; color: var(--muted); font-size: 13px;
}
.footer .support { font-size: 14px; margin: 0 0 8px; }
.footer .links { margin: 0 0 8px; }
.footer .copy { margin: 0; font-size: 12px; }

/* modal */
.modal {
  position: fixed; inset: 0; background: rgba(15,23,42,0.45);
  display: flex; align-items: center; justify-content: center; z-index: 50;
}
.modal.hidden { display: none; }
.modal-box {
  background: #fff; border-radius: 12px; padding: 28px 32px; max-width: 360px; text-align: center;
  box-shadow: 0 12px 40px rgba(0,0,0,0.2);
}
.modal-box h3 { margin: 0 0 10px; color: var(--blue-d); }
.modal-box p { margin: 0 0 18px; color: var(--muted); font-size: 14px; }
.modal-ok {
  background: var(--blue); color: #fff; border: none; padding: 9px 24px;
  border-radius: 8px; font-weight: 600; cursor: pointer;
}
.modal-ok:hover { background: var(--blue-d); }

@media (max-width: 600px) {
  .hero h1 { font-size: 28px; }
  .nav { padding: 14px 18px; }
  .nav nav a { margin-left: 14px; }
}