:root {
  --bg: #f7f6f2;
  --surface: #ffffff;
  --text: #1d1d1b;
  --muted: #5f5e58;
  --line: #e3e1d9;
  --accent: #e8590c;
  --accent-dark: #c2410c;
  --accent-soft: #fff1e6;
  --result-bg: #1d1d1b;
  --result-text: #ffffff;
  --radius: 14px;
  --shadow: 0 1px 2px rgba(0,0,0,.04), 0 4px 16px rgba(0,0,0,.05);
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #151513;
    --surface: #1f1f1c;
    --text: #f1efe8;
    --muted: #a9a79e;
    --line: #34332e;
    --accent: #ff7a2e;
    --accent-dark: #ff9a5c;
    --accent-soft: #2c1d12;
    --result-bg: #2b2a26;
    --result-text: #ffffff;
    --shadow: none;
  }
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.6 system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}
a { color: var(--accent-dark); }
img { max-width: 100%; }
.wrap { max-width: 1040px; margin: 0 auto; padding: 0 16px; }

/* Header / footer */
.site-header { background: var(--surface); border-bottom: 1px solid var(--line); }
.site-header .wrap { display: flex; align-items: center; justify-content: space-between; height: 64px; gap: 16px; }
.logo { font-weight: 800; font-size: 1.3rem; color: var(--text); text-decoration: none; letter-spacing: -.02em; }
.logo span { color: var(--accent); }
.site-header nav a { color: var(--muted); text-decoration: none; margin-left: 20px; font-weight: 500; }
.site-header nav a:hover { color: var(--text); }
.site-footer { border-top: 1px solid var(--line); margin-top: 64px; padding: 32px 0; color: var(--muted); font-size: .9rem; }
.site-footer .wrap { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 12px; }
.site-footer a { color: var(--muted); margin-right: 16px; }

/* Hero */
.hero { padding: 56px 0 32px; }
.hero h1 { font-size: clamp(2rem, 5vw, 3rem); line-height: 1.1; margin: 0 0 12px; letter-spacing: -.03em; }
.hero p { font-size: 1.15rem; color: var(--muted); max-width: 640px; margin: 0; }

/* Tool grid */
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 16px; }
.card {
  display: block; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 20px; text-decoration: none; color: var(--text); box-shadow: var(--shadow);
  transition: transform .15s, border-color .15s;
}
.card:hover { transform: translateY(-2px); border-color: var(--accent); }
.card .icon { font-size: 1.8rem; line-height: 1; }
.card h3 { margin: 12px 0 4px; font-size: 1.1rem; }
.card p { margin: 0; color: var(--muted); font-size: .95rem; }

/* Calculator page */
.breadcrumb { font-size: .9rem; color: var(--muted); padding-top: 24px; }
.breadcrumb a { color: var(--muted); }
.page-title { font-size: clamp(1.8rem, 4vw, 2.4rem); margin: 8px 0 8px; letter-spacing: -.02em; line-height: 1.15; }
.lead { color: var(--muted); font-size: 1.1rem; margin: 0 0 24px; max-width: 680px; }
.calc-layout { display: grid; grid-template-columns: 1fr 340px; gap: 24px; align-items: start; }
@media (max-width: 820px) { .calc-layout { grid-template-columns: 1fr; } }
.panel { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 24px; box-shadow: var(--shadow); }
.units { display: inline-flex; background: var(--bg); border: 1px solid var(--line); border-radius: 999px; padding: 4px; margin-bottom: 20px; }
.units button {
  border: 0; background: transparent; color: var(--muted); font: inherit; font-weight: 600;
  padding: 6px 16px; border-radius: 999px; cursor: pointer;
}
.units button.active { background: var(--accent); color: #fff; }
.fields { display: grid; grid-template-columns: repeat(auto-fill, minmax(180px, 1fr)); gap: 16px; }
.field label { display: block; font-weight: 600; font-size: .92rem; margin-bottom: 6px; }
.field .hint { font-weight: 400; color: var(--muted); }
.input-unit { position: relative; }
.input-unit input, .field select {
  width: 100%; font: inherit; font-size: 1.05rem; padding: 10px 12px; border: 1px solid var(--line);
  border-radius: 10px; background: var(--bg); color: var(--text);
}
.input-unit input { padding-right: 52px; }
.input-unit input:focus, .field select:focus { outline: 2px solid var(--accent); outline-offset: -1px; border-color: transparent; }
.input-unit .u { position: absolute; right: 12px; top: 50%; transform: translateY(-50%); color: var(--muted); font-size: .9rem; pointer-events: none; }
.section-label { grid-column: 1 / -1; font-size: .8rem; text-transform: uppercase; letter-spacing: .08em; color: var(--muted); font-weight: 700; margin-top: 8px; }

.result { background: var(--result-bg); color: var(--result-text); border-radius: var(--radius); padding: 24px; position: sticky; top: 16px; }
.result .label { font-size: .85rem; text-transform: uppercase; letter-spacing: .08em; opacity: .7; }
.result .big { font-size: 2.6rem; font-weight: 800; line-height: 1.1; margin: 4px 0 4px; letter-spacing: -.02em; }
.result .big small { font-size: 1.1rem; font-weight: 600; opacity: .8; }
.result ul { list-style: none; padding: 0; margin: 16px 0 0; border-top: 1px solid rgba(255,255,255,.15); }
.result li { display: flex; justify-content: space-between; gap: 12px; padding: 10px 0; border-bottom: 1px solid rgba(255,255,255,.1); font-size: .95rem; }
.result li b { font-weight: 700; text-align: right; }
.result .note { font-size: .82rem; opacity: .65; margin: 14px 0 0; }

/* Article content */
.content { max-width: 720px; margin-top: 48px; }
.content h2 { font-size: 1.5rem; margin: 40px 0 8px; letter-spacing: -.01em; }
.content h3 { font-size: 1.1rem; margin: 24px 0 4px; }
.content table { border-collapse: collapse; width: 100%; margin: 12px 0; font-size: .95rem; }
.content th, .content td { text-align: left; padding: 8px 10px; border-bottom: 1px solid var(--line); }
.content th { color: var(--muted); font-weight: 600; }
.related { margin-top: 48px; }
.related h2 { font-size: 1.3rem; }

/* Reserved ad slot – stays invisible until ads are added */
.ad-slot:empty { display: none; }
.ad-slot { margin: 24px 0; min-height: 90px; }

.prose { max-width: 720px; padding-top: 32px; }
.prose h1 { font-size: 2.2rem; letter-spacing: -.02em; }

@media (max-width: 520px) {
  .site-header nav a { margin-left: 12px; font-size: .95rem; }
  .panel, .result { padding: 18px; }
  .result .big { font-size: 2.2rem; }
}