/* 无第三方依赖、无网络字体、无追踪脚本。
   目标：首屏即计算器，LCP 尽可能低。 */

:root {
  --ink: #16221d;
  --ink-soft: #4a5a53;
  --line: #d8ded9;
  --bg: #fbfcfa;
  --card: #ffffff;
  --accent: #1b3a2f;
  --accent-soft: #eef4f0;
  --warn: #8a4b12;
  --warn-bg: #fdf5ea;
  --radius: 10px;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

* { box-sizing: border-box; }

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

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 16px/1.6 system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

main { max-width: 46rem; margin: 0 auto; padding: 1.5rem 1.25rem 4rem; }

a { color: var(--accent); }

h1 { font-size: 1.9rem; line-height: 1.2; margin: 0.5rem 0 0.5rem; }
h2 { font-size: 1.25rem; margin: 2rem 0 0.6rem; }
h3 { font-size: 1.02rem; margin: 1.4rem 0 0.4rem; }

.lede { font-size: 1.08rem; color: var(--ink-soft); margin: 0 0 1.5rem; }

/* ---------------- header / footer ---------------- */

.site-header {
  display: flex; align-items: center; justify-content: space-between;
  gap: 1rem; padding: 0.9rem 1.25rem;
  border-bottom: 1px solid var(--line); background: var(--card);
}
.brand { font-weight: 650; text-decoration: none; color: var(--ink); letter-spacing: -0.01em; }
.site-header nav a { margin-left: 1rem; text-decoration: none; color: var(--ink-soft); font-size: 0.94rem; }

.site-footer {
  border-top: 1px solid var(--line); margin-top: 3rem;
  padding: 1.5rem 1.25rem 3rem; max-width: 46rem; margin-inline: auto;
  color: var(--ink-soft); font-size: 0.87rem;
}
.disclaimer { max-width: 42rem; }

.breadcrumb { font-size: 0.84rem; color: var(--ink-soft); margin-bottom: 0.25rem; }
.breadcrumb a { text-decoration: none; }

/* ---------------- calculator ---------------- */

.calc {
  background: var(--card); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 1.25rem; margin-bottom: 2rem;
}

.field { margin-bottom: 1.1rem; }
.field > label { display: block; font-weight: 600; font-size: 0.93rem; margin-bottom: 0.35rem; }

.input-row { display: flex; gap: 0.5rem; }
.input-row.two > input { flex: 1; }
.input-row input[type="number"] {
  flex: 1; min-width: 0; padding: 0.6rem 0.7rem;
  border: 1px solid var(--line); border-radius: 8px; font-size: 1rem;
  background: #fff; color: var(--ink);
}
.input-row select {
  padding: 0.6rem 0.5rem; border: 1px solid var(--line);
  border-radius: 8px; background: #fff; font-size: 0.92rem; color: var(--ink);
}
.unit-static { align-self: center; color: var(--ink-soft); font-size: 0.9rem; padding: 0 0.35rem; }

input:focus-visible, select:focus-visible, button:focus-visible {
  outline: 2px solid var(--accent); outline-offset: 1px;
}

.hint { font-size: 0.83rem; color: var(--ink-soft); margin: 0.35rem 0 0; }

.presets { display: flex; flex-wrap: wrap; gap: 0.4rem; margin-top: 0.5rem; }
.preset {
  font-size: 0.82rem; padding: 0.3rem 0.6rem; border-radius: 999px;
  border: 1px solid var(--line); background: var(--accent-soft); color: var(--accent);
  cursor: pointer;
}
.preset:hover { background: #e2ede7; }

.advanced { margin: 0.5rem 0 1.1rem; border-top: 1px dashed var(--line); padding-top: 0.8rem; }
.advanced summary { cursor: pointer; font-weight: 600; font-size: 0.92rem; color: var(--ink-soft); }
.advanced .field { margin-top: 1rem; }

.actions { display: flex; gap: 0.6rem; }
button.primary {
  background: var(--accent); color: #fff; border: 0; border-radius: 8px;
  padding: 0.7rem 1.3rem; font-size: 1rem; font-weight: 600; cursor: pointer;
}
button.primary:hover { background: #143026; }
button.ghost {
  background: transparent; border: 1px solid var(--line); border-radius: 8px;
  padding: 0.7rem 1rem; font-size: 0.95rem; color: var(--ink-soft); cursor: pointer;
}

/* ---------------- results ---------------- */

.results { margin-top: 1.4rem; border-top: 1px solid var(--line); padding-top: 1.2rem; }
.results h2 { margin-top: 0; font-size: 1.1rem; }

.results-table, .steps, .const { width: 100%; border-collapse: collapse; }
.results-table th, .results-table td,
.steps th, .steps td, .const th, .const td {
  text-align: left; padding: 0.5rem 0.6rem; border-bottom: 1px solid var(--line);
  vertical-align: top; font-size: 0.94rem;
}
.results-table th, .steps th, .const th {
  font-weight: 600; color: var(--ink-soft); width: 42%;
}
.results-table tr.emphasis td { font-size: 1.15rem; font-weight: 650; }
.results-table .alt { color: var(--ink-soft); font-size: 0.85em; margin-left: 0.4rem; }
.results-table .unit { color: var(--ink-soft); font-size: 0.85em; }
.results-table .note, .assumption .note {
  display: block; font-size: 0.78rem; color: var(--ink-soft); font-weight: 400;
}
.assumption { font-size: 0.85rem; color: var(--ink-soft); margin-top: 0.9rem; }
.ask-supplier {
  font-size: 0.85rem; background: var(--accent-soft); border-left: 3px solid var(--accent);
  padding: 0.6rem 0.8rem; border-radius: 0 6px 6px 0; margin-top: 0.6rem;
}
.error {
  color: #8a1c1c; background: #fdeeee; border-left: 3px solid #8a1c1c;
  padding: 0.7rem 0.9rem; border-radius: 0 6px 6px 0; margin: 0;
}
.caveat {
  background: var(--warn-bg); border-left: 3px solid var(--warn);
  padding: 0.7rem 0.9rem; border-radius: 0 6px 6px 0; font-size: 0.9rem;
}

/* ---------------- content ---------------- */

.formula { padding-left: 1.2rem; }
.formula code { font-family: var(--mono); background: var(--accent-soft); padding: 0.1rem 0.35rem; border-radius: 4px; }
.why-range { font-size: 0.95rem; }
.sources { padding-left: 1.2rem; font-size: 0.9rem; }
.sources li { margin-bottom: 0.6rem; }
.sources q { color: var(--ink-soft); }

.faq details {
  border: 1px solid var(--line); border-radius: 8px; padding: 0.7rem 0.9rem;
  margin-bottom: 0.5rem; background: var(--card);
}
.faq summary { cursor: pointer; font-weight: 600; }
.faq .answer { margin-top: 0.6rem; font-size: 0.95rem; }
.faq .answer p:first-child { margin-top: 0; }

.related ul { list-style: none; padding: 0; display: flex; flex-wrap: wrap; gap: 0.5rem; }
.related a {
  display: inline-block; padding: 0.4rem 0.7rem; border: 1px solid var(--line);
  border-radius: 999px; text-decoration: none; font-size: 0.9rem; background: var(--card);
}

/* ---------------- hub ---------------- */

.hub-note { color: var(--ink-soft); }
.cards { list-style: none; padding: 0; display: grid; gap: 0.75rem; grid-template-columns: 1fr; }
@media (min-width: 34rem) { .cards { grid-template-columns: 1fr 1fr; } }
.card a {
  display: block; padding: 1rem; border: 1px solid var(--line); border-radius: var(--radius);
  background: var(--card); text-decoration: none; color: inherit; height: 100%;
}
.card a:hover { border-color: var(--accent); }
.card h3 { margin: 0 0 0.3rem; font-size: 1rem; }
.card p { margin: 0; font-size: 0.88rem; color: var(--ink-soft); }

@media (max-width: 30rem) {
  h1 { font-size: 1.55rem; }
  main { padding: 1rem 1rem 3rem; }
  .results-table th, .results-table td { font-size: 0.88rem; }
}