:root {
  --bg: #ffffff;
  --bg-soft: #f8f9fb;
  --panel: #ffffff;
  --text: #111827;
  --text-2: #4b5563;
  --text-3: #6b7280;
  --line: #e5e7eb;
  --line-2: #d1d5db;
  --accent: #6d28d9;
  --accent-soft: #f3efff;
  --accent-2: #0ea5e9;
  --ok: #047857;
  --warn: #b45309;
  --radius: 14px;
  --shadow: 0 1px 2px rgba(16, 24, 40, .04), 0 8px 24px -16px rgba(16, 24, 40, .18);
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0c0d11;
    --bg-soft: #12141a;
    --panel: #15171e;
    --text: #f3f4f6;
    --text-2: #c3c7cf;
    --text-3: #9aa1ad;
    --line: #262a33;
    --line-2: #363b47;
    --accent: #a78bfa;
    --accent-soft: #1d1a2e;
    --shadow: 0 1px 2px rgba(0, 0, 0, .3), 0 8px 24px -16px rgba(0, 0, 0, .6);
  }
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial,
    "Hiragino Sans", "Hiragino Kaku Gothic ProN", "Yu Gothic", Meiryo,
    "Apple SD Gothic Neo", "Malgun Gothic", "Noto Sans JP", "Noto Sans KR", sans-serif;
  font-size: 16px;
  line-height: 1.65;
}

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

.wrap { width: 100%; max-width: 1080px; margin: 0 auto; padding: 0 20px; }
.narrow { max-width: 760px; }

/* header */
.site-header {
  position: sticky; top: 0; z-index: 20;
  background: var(--bg);
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid var(--line);
}
.header-inner { display: flex; align-items: center; gap: 24px; height: 62px; }
.logo { display: flex; align-items: center; gap: 10px; color: var(--text); font-weight: 600; }
.logo:hover { text-decoration: none; }
.logo-mark {
  width: 26px; height: 26px; border-radius: 8px; flex: none;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  display: grid; place-items: center; color: #fff; font-size: 14px; font-weight: 700;
}
.logo small { display: block; font-size: 11px; font-weight: 400; color: var(--text-3); letter-spacing: .02em; }
.nav { display: flex; gap: 20px; margin-left: auto; }
.nav a { color: var(--text-2); font-size: 14.5px; }
.nav a:hover { color: var(--text); text-decoration: none; }

/* 语言切换器 */
.lang-switch {
  display: flex; align-items: center; gap: 2px; flex: none;
  border: 1px solid var(--line); border-radius: 999px; padding: 2px;
}
.lang-switch a {
  padding: 3px 9px; border-radius: 999px; font-size: 11.5px; font-weight: 600;
  letter-spacing: .04em; color: var(--text-3); line-height: 1.5;
}
.lang-switch a:hover { color: var(--text); text-decoration: none; background: var(--bg-soft); }
.lang-switch a.active { background: var(--accent); color: #fff; }

@media (max-width: 900px) {
  .header-inner { gap: 12px; }
  .nav { gap: 12px; overflow-x: auto; scrollbar-width: none; }
  .nav::-webkit-scrollbar { display: none; }
  .nav a { white-space: nowrap; }
}
@media (max-width: 720px) {
  .header-inner { gap: 10px; height: auto; min-height: 58px; flex-wrap: wrap; padding: 8px 0; }
  .nav { gap: 12px; order: 3; width: 100%; margin-left: 0; padding-bottom: 2px; }
  .nav a { font-size: 13px; }
  .logo small { display: none; }
  .lang-switch { margin-left: auto; }
}

/* hero */
.hero { padding: 56px 0 40px; }
.hero h1 { margin: 0 0 14px; font-size: clamp(28px, 4vw, 40px); line-height: 1.2; letter-spacing: -.02em; font-weight: 600; }
.hero p { margin: 0; max-width: 62ch; color: var(--text-2); font-size: 17px; }
.eyebrow {
  display: inline-block; margin-bottom: 14px; padding: 4px 10px; border-radius: 999px;
  background: var(--accent-soft); color: var(--accent); font-size: 12.5px; font-weight: 600;
  letter-spacing: .04em; text-transform: uppercase;
}

/* section */
.section { padding: 8px 0 48px; }
.section-head { display: flex; align-items: baseline; justify-content: space-between; gap: 16px; margin-bottom: 18px; }
.section-head h2 { margin: 0; font-size: 22px; font-weight: 600; letter-spacing: -.01em; }
.section-head span { color: var(--text-3); font-size: 14px; }

/* tool cards */
.tool-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 16px; }
.tool-card {
  display: block; padding: 22px; border: 1px solid var(--line); border-radius: var(--radius);
  background: var(--panel); box-shadow: var(--shadow); transition: .18s; color: inherit;
}
.tool-card:hover { transform: translateY(-2px); border-color: var(--line-2); text-decoration: none; }
.tool-card h3 { margin: 0 0 8px; font-size: 17px; font-weight: 600; }
.tool-card p { margin: 0; color: var(--text-3); font-size: 14.5px; line-height: 1.6; }
.tool-card .go { display: inline-block; margin-top: 14px; font-size: 13.5px; color: var(--accent); font-weight: 500; }
.tool-icon {
  width: 34px; height: 34px; border-radius: 10px; background: var(--accent-soft);
  display: grid; place-items: center; margin-bottom: 14px; color: var(--accent);
}

/* calculator */
.calc {
  display: grid; grid-template-columns: 1.05fr .95fr; gap: 0;
  border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden;
  background: var(--panel); box-shadow: var(--shadow); margin-bottom: 44px;
}
@media (max-width: 820px) { .calc { grid-template-columns: 1fr; } }
.calc-form { padding: 26px; display: grid; gap: 16px; align-content: start; }
.calc-out {
  padding: 26px; background: var(--bg-soft); border-left: 1px solid var(--line);
  display: flex; flex-direction: column; justify-content: center; gap: 14px;
}
@media (max-width: 820px) { .calc-out { border-left: none; border-top: 1px solid var(--line); } }

.field label { display: block; font-size: 13.5px; font-weight: 500; color: var(--text-2); margin-bottom: 6px; }
.field .hint { display: block; margin-top: 5px; font-size: 12.5px; color: var(--text-3); }
input[type="number"], input[type="text"], select {
  width: 100%; height: 42px; padding: 0 12px; font-size: 15px; color: var(--text);
  background: var(--bg); border: 1px solid var(--line-2); border-radius: 9px;
  font-family: inherit; appearance: none;
}
select { background-image: none; cursor: pointer; }
input:focus, select:focus { outline: 2px solid color-mix(in srgb, var(--accent) 45%, transparent); outline-offset: 1px; border-color: var(--accent); }
.row-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; }

.out-label { font-size: 12.5px; text-transform: uppercase; letter-spacing: .06em; color: var(--text-3); font-weight: 600; }
.out-main { font-size: 40px; font-weight: 600; line-height: 1.1; letter-spacing: -.02em; color: var(--text); margin: 0; }
.out-sub { margin: 0; color: var(--text-2); font-size: 14.5px; }
.out-divider { height: 1px; background: var(--line); margin: 4px 0; }
.kv { display: flex; justify-content: space-between; gap: 12px; font-size: 14.5px; }
.kv span:first-child { color: var(--text-3); }
.kv span:last-child { font-weight: 500; font-variant-numeric: tabular-nums; }

/* prose */
.prose { max-width: 72ch; }
.prose h2 { margin: 40px 0 12px; font-size: 23px; font-weight: 600; letter-spacing: -.01em; }
.prose h3 { margin: 28px 0 8px; font-size: 18px; font-weight: 600; }
.prose p, .prose li { color: var(--text-2); font-size: 16px; line-height: 1.72; }
.prose ul, .prose ol { padding-left: 22px; }
.prose li { margin: 6px 0; }
.prose strong { color: var(--text); font-weight: 600; }
.formula {
  margin: 16px 0; padding: 14px 16px; background: var(--bg-soft); border: 1px solid var(--line);
  border-radius: 10px; font-family: var(--mono); font-size: 14px; color: var(--text);
  overflow-x: auto;
}
.callout {
  margin: 20px 0; padding: 16px 18px; border-radius: 10px;
  background: var(--accent-soft); border: 1px solid color-mix(in srgb, var(--accent) 22%, transparent);
  font-size: 15px; color: var(--text-2);
}
.callout strong { color: var(--text); }
table.data { width: 100%; border-collapse: collapse; margin: 16px 0; font-size: 14.5px; }
table.data th, table.data td { text-align: left; padding: 9px 12px; border-bottom: 1px solid var(--line); }
table.data th { color: var(--text-3); font-weight: 500; font-size: 13px; text-transform: uppercase; letter-spacing: .04em; }
table.data td { color: var(--text-2); font-variant-numeric: tabular-nums; }

/* faq */
.faq { margin: 12px 0 0; border-top: 1px solid var(--line); }
.faq details { border-bottom: 1px solid var(--line); padding: 4px 0; }
.faq summary {
  cursor: pointer; padding: 14px 0; font-size: 16px; font-weight: 500; color: var(--text);
  list-style: none; display: flex; justify-content: space-between; gap: 16px;
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after { content: "+"; color: var(--text-3); font-weight: 400; }
.faq details[open] summary::after { content: "−"; }
.faq details p { margin: 0 0 16px; color: var(--text-2); font-size: 15.5px; }

/* related */
.related { margin: 48px 0 0; padding: 24px; border-radius: var(--radius); background: var(--bg-soft); border: 1px solid var(--line); }
.related h2 { margin: 0 0 14px; font-size: 16px; font-weight: 600; }
.related ul { margin: 0; padding: 0; list-style: none; display: grid; gap: 10px; }
.related li a { font-size: 15px; }

/* breadcrumb */
.crumb { font-size: 13px; color: var(--text-3); margin-bottom: 18px; }
.crumb a { color: var(--text-3); }
.crumb a:hover { color: var(--accent); }

/* footer */
.site-footer { margin-top: 64px; border-top: 1px solid var(--line); background: var(--bg-soft); }
.footer-inner { padding: 36px 0; display: grid; grid-template-columns: 1.4fr 1fr 1fr; gap: 28px; }
@media (max-width: 720px) { .footer-inner { grid-template-columns: 1fr; gap: 22px; } }
.footer-inner h4 { margin: 0 0 10px; font-size: 13px; text-transform: uppercase; letter-spacing: .06em; color: var(--text-3); font-weight: 600; }
.footer-inner ul { margin: 0; padding: 0; list-style: none; display: grid; gap: 7px; }
.footer-inner a { color: var(--text-2); font-size: 14.5px; }
.footer-inner .sibling-link { color: var(--accent); }
.footer-note { padding: 0 0 30px; color: var(--text-3); font-size: 13px; line-height: 1.7; }
.disclaimer { color: var(--text-3); font-size: 13.5px; margin-top: 12px; }

/* article list */
.page-list { margin: 0; padding: 0; list-style: none; display: grid; gap: 14px; }
.page-list li { padding-bottom: 14px; border-bottom: 1px solid var(--line); }
.page-list a { font-size: 16.5px; font-weight: 500; }
.page-list p { margin: 4px 0 0; color: var(--text-3); font-size: 14.5px; }

@media (max-width: 560px) {
  .row-2 { grid-template-columns: 1fr; }
  table.data { display: block; overflow-x: auto; white-space: nowrap; }
  .hero { padding: 34px 0 26px; }
  .calc-form, .calc-out { padding: 20px; }
  .out-main { font-size: 34px; }
}