:root {
  --bg: #f4f6fa;
  --panel: #ffffff;
  --panel-2: #f1f4f9;
  --border: #e1e6ee;
  --text: #18223a;
  --muted: #5b6678;
  --accent: #2563eb;
  --accent-soft: #e9f0ff;
  --ok: #0f9d58;
  --radius: 12px;
  --shadow: 0 1px 3px rgba(20, 35, 70, 0.06), 0 6px 18px rgba(20, 35, 70, 0.05);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

header.site {
  border-bottom: 1px solid var(--border);
  padding: 14px 20px;
  display: flex;
  align-items: center;
  gap: 14px;
  position: sticky;
  top: 0;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(8px);
  z-index: 10;
}
header.site .brand { font-weight: 700; font-size: 1.2rem; letter-spacing: 0.3px; color: var(--text); }
header.site nav { margin-left: auto; display: flex; gap: 16px; font-size: 0.92rem; }
header.site nav a { color: var(--muted); }
header.site nav a:hover { color: var(--accent); }

.container {
  max-width: 1080px;
  margin: 0 auto;
  padding: 28px 20px 60px;
  display: grid;
  grid-template-columns: 1fr 260px;
  gap: 32px;
}

main { min-width: 0; }

h1 { font-size: 1.7rem; margin: 0 0 6px; }
.lede { color: var(--muted); margin: 0 0 24px; }

.calc {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 14px;
  box-shadow: var(--shadow);
}
.field { display: flex; flex-direction: column; gap: 6px; }
.field label { font-size: 0.85rem; color: var(--muted); font-weight: 500; }
.field input, .field select {
  background: var(--panel-2);
  border: 1px solid var(--border);
  color: var(--text);
  border-radius: 8px;
  padding: 10px 12px;
  font-size: 1rem;
}
.field input:focus, .field select:focus {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
  border-color: var(--accent);
}

.result {
  margin-top: 22px;
  background: linear-gradient(180deg, var(--accent-soft), #ffffff);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px;
  box-shadow: var(--shadow);
}
.result .big { font-size: 2.1rem; font-weight: 700; color: var(--accent); }
.result .row { display: flex; justify-content: space-between; padding: 6px 0; border-top: 1px solid var(--border); font-size: 0.95rem; }
.result .row span:last-child { font-variant-numeric: tabular-nums; font-weight: 600; color: var(--text); }

.work {
  margin-top: 18px;
  background: var(--panel);
  border: 1px dashed var(--border);
  border-radius: var(--radius);
  padding: 16px;
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 0.86rem;
  color: var(--muted);
  white-space: pre-wrap;
}

section.block { margin-top: 34px; }
section.block h2 { font-size: 1.2rem; }
section.block p { color: var(--muted); }
.faq details { border: 1px solid var(--border); border-radius: 8px; padding: 10px 14px; margin-bottom: 8px; background: var(--panel); }
.faq summary { cursor: pointer; font-weight: 600; }

aside.related { font-size: 0.9rem; }
aside.related h3 { font-size: 0.95rem; color: var(--muted); text-transform: uppercase; letter-spacing: 0.5px; }
aside.related ul { list-style: none; padding: 0; margin: 0; }
aside.related li { padding: 6px 0; border-bottom: 1px solid var(--border); }

.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 16px; }
.card { background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius); padding: 18px; display: block; color: var(--text); box-shadow: var(--shadow); }
.card:hover { border-color: var(--accent); text-decoration: none; box-shadow: 0 2px 8px rgba(37, 99, 235, 0.12); }
.card .t { font-weight: 600; }
.card .d { color: var(--muted); font-size: 0.85rem; margin-top: 4px; }

footer.site { border-top: 1px solid var(--border); padding: 22px 20px; color: var(--muted); font-size: 0.85rem; text-align: center; }
footer.site a { color: var(--muted); margin: 0 8px; }

@media (max-width: 820px) {
  .container { grid-template-columns: 1fr; }
  .calc { grid-template-columns: 1fr; }
}