:root {
  --bg: #f4f6fb;
  --surface: #ffffff;
  --ink: #121826;
  --muted: #667085;
  --line: #e4e8f0;
  --primary: #2563eb;
  --primary-ink: #ffffff;
  --accent: #0f766e;
  --pink: #e11d8f;
  --warn: #c2410c;
  --shadow: 0 10px 30px rgba(18, 24, 38, 0.06);
  --radius: 16px;
}

html.dark {
  --bg: #0f1220;
  --surface: #181c2e;
  --ink: #eef2ff;
  --muted: #9aa3b8;
  --line: #2a3148;
  --primary: #3b82f6;
  --primary-ink: #ffffff;
  --accent: #2dd4bf;
  --pink: #f472b6;
  --warn: #fb923c;
  --shadow: 0 12px 32px rgba(0, 0, 0, 0.28);
}

* { box-sizing: border-box; }
html, body { margin: 0; min-height: 100%; }
body {
  font: 15px/1.55 "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  color: var(--ink);
  background:
    radial-gradient(1200px 500px at 10% -10%, rgba(37, 99, 235, 0.08), transparent 50%),
    var(--bg);
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 14px 24px;
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--line);
}
.brand { display: flex; flex-direction: column; gap: 2px; }
.brand p { margin: 0; font-size: 18px; font-weight: 650; letter-spacing: 0.02em; }
.brand span { color: var(--muted); font-size: 12px; }
.theme-btn {
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--ink);
  border-radius: 999px;
  height: 36px;
  padding: 0 14px;
  cursor: pointer;
}

.wrap {
  max-width: 1180px;
  margin: 0 auto;
  padding: 28px 20px 64px;
}

.hero h1 {
  margin: 0 0 8px;
  font-size: 28px;
  letter-spacing: -0.02em;
}
.hero p { margin: 0 0 22px; color: var(--muted); max-width: 52em; }

.card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 20px;
}

.seg {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 18px;
}
.seg button {
  border: 1px solid var(--line);
  background: transparent;
  color: var(--ink);
  border-radius: 999px;
  padding: 8px 14px;
  cursor: pointer;
}
.seg button.active {
  background: var(--primary);
  border-color: var(--primary);
  color: var(--primary-ink);
}

.grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px 16px;
}
[hidden] { display: none !important; }
.pair {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px 16px;
  grid-column: 1 / -1;
}
.field { display: flex; flex-direction: column; gap: 6px; }
.field.full { grid-column: 1 / -1; }
.field label { font-size: 13px; color: var(--muted); }
.control {
  display: flex;
  align-items: center;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: color-mix(in srgb, var(--bg) 65%, var(--surface));
  overflow: hidden;
}
.control input, .control select {
  flex: 1;
  border: 0;
  outline: none;
  background: transparent;
  color: var(--ink);
  height: 42px;
  padding: 0 12px;
  font: inherit;
}
.control .unit {
  padding: 0 12px;
  color: var(--muted);
  font-size: 13px;
  border-left: 1px solid var(--line);
  height: 42px;
  display: flex;
  align-items: center;
}
.hint { color: var(--warn); font-size: 13px; min-height: 1.2em; margin: 8px 0 0; }

.calc-btn {
  margin-top: 16px;
  width: 100%;
  height: 46px;
  border: 0;
  border-radius: 12px;
  background: linear-gradient(90deg, #2563eb, #4f46e5);
  color: #fff;
  font-size: 16px;
  font-weight: 650;
  cursor: pointer;
}

.results { margin-top: 28px; display: none; }
.results.show { display: block; }
.tabs {
  display: flex;
  gap: 8px;
  margin-bottom: 14px;
}
.tabs button {
  flex: 1;
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--ink);
  border-radius: 12px;
  padding: 10px 12px;
  cursor: pointer;
  font-weight: 650;
}
.tabs button.active {
  border-color: var(--primary);
  box-shadow: inset 0 0 0 1px var(--primary);
}

.pay-card {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 16px;
}
.pay-main {
  background: linear-gradient(135deg, #1d4ed8, #2563eb 55%, #0ea5e9);
  color: #fff;
  border-radius: 16px;
  padding: 22px;
}
.pay-main.principal {
  background: linear-gradient(135deg, #0f766e, #14b8a6 55%, #22c55e);
}
.pay-main .k { opacity: 0.85; font-size: 13px; }
.pay-main .v {
  font-size: 36px;
  font-weight: 750;
  letter-spacing: -0.03em;
  margin: 4px 0 8px;
}
.pay-main .sub { font-size: 13px; opacity: 0.9; }
.pay-pair { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin-top: 14px; }
.pay-pair div {
  background: rgba(255,255,255,0.14);
  border-radius: 10px;
  padding: 10px;
}
.pay-pair .k { font-size: 12px; opacity: 0.85; }
.pay-pair .v { font-size: 18px; font-weight: 700; }

.comp {
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 18px;
  background: var(--surface);
}
.comp h3 { margin: 0 0 4px; font-size: 16px; }
.comp .note { color: var(--muted); font-size: 12px; margin-bottom: 14px; }
.stats { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.stat {
  background: color-mix(in srgb, var(--bg) 80%, var(--surface));
  border-radius: 12px;
  padding: 10px 12px;
}
.stat .k { color: var(--muted); font-size: 12px; }
.stat .v { font-weight: 700; font-size: 16px; }
.chart-row { display: flex; align-items: center; gap: 16px; margin-top: 14px; }
.chart { width: 92px; height: 92px; }
.legend { font-size: 13px; color: var(--muted); }
.legend b { color: var(--ink); }

.table-wrap {
  margin-top: 18px;
  border: 1px solid var(--line);
  border-radius: 16px;
  overflow: hidden;
  background: var(--surface);
}
.table-head {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 12px 14px;
  border-bottom: 1px solid var(--line);
}
.table-head select {
  height: 34px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
  color: var(--ink);
  padding: 0 8px;
}
.table-scroll { max-height: 420px; overflow: auto; }
table { width: 100%; border-collapse: collapse; font-size: 13px; }
th, td { padding: 8px 10px; text-align: right; border-bottom: 1px solid var(--line); }
th:first-child, td:first-child { text-align: left; }
th { position: sticky; top: 0; background: var(--surface); color: var(--muted); font-weight: 600; }

.explain, .faq {
  margin-top: 28px;
  color: var(--muted);
  font-size: 13px;
}
.explain h2, .faq h2 { color: var(--ink); font-size: 18px; margin: 0 0 10px; }
.explain h3, .faq h3 { color: var(--ink); font-size: 15px; margin: 16px 0 6px; }
.faq details {
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--surface);
  padding: 12px 14px;
  margin-bottom: 8px;
}
.faq summary { cursor: pointer; font-weight: 650; color: var(--ink); }
.faq details p { margin: 8px 0 0; }
.site-footer {
  margin-top: 36px;
  padding-top: 16px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 12px;
}

@media (max-width: 860px) {
  .grid, .pay-card, .stats, .pair { grid-template-columns: 1fr; }
  .hero h1 { font-size: 22px; }
}