/* 学脉 · the public site (xuemai.net). One page, no scripts: the deep sea of the map. */
:root {
  --bg: #041a2e;
  --bg2: #06223a;
  --panel: rgba(18, 64, 96, 0.45);
  --line: rgba(120, 200, 230, 0.22);
  --text: #e6f4fa;
  --muted: #9fc0d0;
  --accent: #5fe3f0;
  --accent-ink: #032033;
  --gold: #ffd36b;
  color-scheme: dark;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background:
    radial-gradient(1200px 600px at 70% -10%, rgba(40, 150, 200, 0.35), transparent 60%),
    linear-gradient(180deg, var(--bg2) 0%, var(--bg) 40%, #020f1c 100%);
  background-color: var(--bg);
  color: var(--text);
  font: 16px/1.75 -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", sans-serif;
  -webkit-text-size-adjust: 100%;
}
a { color: var(--accent); }
b { color: #fff; }

.top {
  position: sticky; top: 0; z-index: 5;
  display: flex; align-items: center; justify-content: space-between; gap: 12px;
  padding: 10px max(16px, calc((100vw - 1080px) / 2));
  background: rgba(4, 26, 46, 0.82);
  backdrop-filter: blur(10px); -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}
.brand { display: flex; align-items: center; gap: 8px; color: var(--text); text-decoration: none; font-weight: 700; font-size: 20px; letter-spacing: 2px; }
.logo { width: 28px; height: 28px; fill: var(--accent); }
.logo path { fill: none; stroke: var(--accent); stroke-width: 2.4; stroke-linecap: round; }
.top nav { display: flex; gap: 18px; }
.top nav a { color: var(--muted); text-decoration: none; font-size: 15px; }
.top nav a:hover { color: var(--text); }

main { max-width: 1080px; margin: 0 auto; padding: 0 16px; }
section { padding: 56px 0; }
h1 { font-size: clamp(30px, 5.2vw, 48px); line-height: 1.25; margin: 6px 0 16px; letter-spacing: 1px; }
h2 { font-size: clamp(24px, 3.6vw, 32px); margin: 0 0 24px; text-align: center; }
h3 { font-size: 21px; margin: 0 0 10px; }
.eyebrow { color: var(--accent); font-weight: 600; letter-spacing: 3px; margin: 0; }
.lede { font-size: 18px; color: var(--muted); max-width: 34em; }
.small { color: var(--muted); font-size: 14px; }
.sub { color: var(--muted); text-align: center; margin: -12px auto 28px; max-width: 36em; }

.btn {
  display: inline-block; padding: 12px 22px; border-radius: 999px;
  border: 1px solid var(--accent); color: var(--accent);
  text-decoration: none; font-weight: 600; text-align: center;
}
.btn.primary { background: var(--accent); color: var(--accent-ink); }
.btn:hover { filter: brightness(1.1); }
.btn.off { border-color: var(--line); color: var(--muted); cursor: default; }
.cta { display: flex; flex-wrap: wrap; gap: 12px; margin: 26px 0 10px; }

.phone {
  margin: 0; width: 270px; max-width: 72vw; flex: none;
  border-radius: 30px; padding: 8px; background: #0b2c45;
  border: 1px solid var(--line);
  box-shadow: 0 24px 60px rgba(0, 0, 0, 0.5), 0 0 60px rgba(95, 227, 240, 0.12);
}
.phone img { display: block; width: 100%; height: auto; border-radius: 22px; }

.hero { display: flex; align-items: center; justify-content: space-between; gap: 40px; padding-top: 48px; }
.hero-text { flex: 1; min-width: 0; }

.feature { display: flex; align-items: center; gap: 48px; padding: 28px 0; }
.feature.flip { flex-direction: row-reverse; }
.feature > div { flex: 1; min-width: 0; }
.feature p { color: var(--muted); }
.steps { color: var(--muted); padding-left: 1.4em; margin: 0; }
.steps li { margin: 4px 0; }

.table-wrap { overflow-x: auto; border: 1px solid var(--line); border-radius: 14px; background: var(--panel); }
table { width: 100%; border-collapse: collapse; min-width: 520px; }
th, td { padding: 12px 14px; text-align: left; border-bottom: 1px solid var(--line); white-space: nowrap; }
th { color: var(--muted); font-weight: 600; font-size: 14px; }
tbody tr:last-child td { border-bottom: 0; }
td:first-child { color: var(--accent); font-weight: 600; }
td:last-child, th:last-child { text-align: right; }

.cards { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; }
.card {
  display: flex; flex-direction: column; gap: 6px;
  padding: 22px 18px; border-radius: 18px;
  background: var(--panel); border: 1px solid var(--line);
}
.card.best { border-color: var(--accent); box-shadow: 0 0 0 1px var(--accent), 0 0 40px rgba(95, 227, 240, 0.15); }
.card h3 { margin: 0; }
.price { font-size: 30px; font-weight: 700; color: #fff; margin: 0; }
.price s { font-size: 16px; color: var(--muted); font-weight: 400; margin-left: 6px; }
.tag { margin: 0; color: var(--gold); font-size: 13px; font-weight: 600; }
.card ul { color: var(--muted); padding-left: 1.2em; margin: 8px 0 16px; flex: 1; font-size: 15px; }
.card .btn { width: 100%; }
.card .link { text-align: center; font-size: 14px; margin-top: 4px; }

.faq { max-width: 760px; margin: 0 auto; }
details { border-bottom: 1px solid var(--line); padding: 14px 4px; }
summary { cursor: pointer; font-weight: 600; font-size: 17px; }
details p { color: var(--muted); margin: 10px 0 0; }

footer { text-align: center; color: var(--muted); font-size: 13px; padding: 40px 16px 56px; border-top: 1px solid var(--line); margin-top: 32px; }
footer p { margin: 4px 0; }

@media (max-width: 900px) {
  .cards { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 720px) {
  section { padding: 40px 0; }
  .top nav { gap: 12px; }
  .top nav a { font-size: 14px; }
  .hero { flex-direction: column; text-align: left; padding-top: 32px; }
  h1 { font-size: 26px; letter-spacing: 0; }
  .hero-phone { width: 230px; }
  .feature, .feature.flip { flex-direction: column; gap: 24px; }
  .feature .phone { width: 230px; }
  .cards { grid-template-columns: 1fr; }
}
@media (max-width: 380px) {
  .top nav a:nth-child(1) { display: none; }
}