:root {
  --bg: #f6f8f9;
  --surface: #ffffff;
  --surface-2: #eef3f4;
  --text: #15232b;
  --muted: #546570;
  --border: #d6e0e4;
  --accent: #0b7a75;
  --accent-ink: #ffffff;
  --accent-soft: #e0f2f0;
  --warn: #9a5b00;
  --warn-soft: #fff4e0;
  --radius: 14px;
  --shadow: 0 1px 2px rgba(16, 40, 48, .06), 0 8px 24px rgba(16, 40, 48, .06);
  --max: 1080px;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0f171b; --surface: #16222a; --surface-2: #1c2b34; --text: #e6eef1;
    --muted: #9db0ba; --border: #2a3c46; --accent: #3cc2b9; --accent-ink: #062523;
    --accent-soft: #123a3a; --warn: #f2b45a; --warn-soft: #3a2a10; color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #0f171b; --surface: #16222a; --surface-2: #1c2b34; --text: #e6eef1;
  --muted: #9db0ba; --border: #2a3c46; --accent: #3cc2b9; --accent-ink: #062523;
  --accent-soft: #123a3a; --warn: #f2b45a; --warn-soft: #3a2a10; color-scheme: dark;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0; background: var(--bg); color: var(--text);
  font: 17px/1.65 system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}
img { max-width: 100%; height: auto; display: block; }
a { color: var(--accent); text-underline-offset: 2px; }
.wrap { max-width: var(--max); margin: 0 auto; padding: 0 16px; }

/* header */
.site-header { background: var(--surface); border-bottom: 1px solid var(--border); }
.site-header .wrap { display: flex; align-items: center; justify-content: space-between; gap: 16px; min-height: 60px; flex-wrap: wrap; }
.brand { font-weight: 700; color: var(--text); text-decoration: none; display: flex; align-items: center; gap: 8px; }
.brand-mark { width: 26px; height: 26px; border-radius: 8px; background: var(--accent); display: inline-grid; place-items: center; color: var(--accent-ink); font-size: 14px; }
.site-nav { display: flex; gap: 4px; flex-wrap: wrap; }
.site-nav a { color: var(--muted); text-decoration: none; padding: 6px 10px; border-radius: 8px; font-size: 15px; }
.site-nav a:hover, .site-nav a[aria-current="page"] { color: var(--text); background: var(--surface-2); }

/* breadcrumb */
.crumbs { font-size: 14px; color: var(--muted); margin: 18px 0 0; }
.crumbs a { color: var(--muted); }

/* hero */
.hero { padding: 20px 0 8px; }
.hero h1 { font-size: clamp(30px, 5vw, 44px); line-height: 1.15; margin: 8px 0 12px; letter-spacing: -.01em; }
.lead { font-size: 18px; color: var(--muted); max-width: 760px; margin: 0; }

/* calculator */
.tool { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow); padding: 22px; margin: 24px 0 8px; display: grid; grid-template-columns: 1.05fr 1fr; gap: 24px; }
@media (max-width: 820px) { .tool { grid-template-columns: 1fr; padding: 16px; } }
.tool > * { min-width: 0; }
.tool h2 { font-size: 20px; margin: 0 0 4px; }
.field { margin: 14px 0 0; }
.field > label, .field > .label { display: block; font-weight: 600; font-size: 15px; margin-bottom: 6px; }
.hint { font-size: 13px; color: var(--muted); margin: 4px 0 0; }
.input-row { display: flex; gap: 8px; }
.input-row input { flex: 1; min-width: 0; }
input[type="number"], select {
  width: 100%; font: inherit; color: var(--text); background: var(--surface-2);
  border: 1px solid var(--border); border-radius: 10px; padding: 10px 12px; min-height: 46px;
}
select { width: auto; max-width: 100%; }
input:focus, select:focus, button:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }
.chips { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 8px; }
.chip { font: inherit; font-size: 14px; border: 1px solid var(--border); background: var(--surface); color: var(--text); border-radius: 999px; padding: 4px 12px; cursor: pointer; min-height: 32px; }
.chip:hover { border-color: var(--accent); }
.chip[aria-pressed="true"] { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }

.results { background: var(--accent-soft); border-radius: 12px; padding: 18px; align-self: start; }
.big { font-size: 15px; color: var(--muted); margin: 0; }
.big strong { display: block; font-size: 44px; line-height: 1.1; color: var(--text); letter-spacing: -.02em; }
.stats { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin: 16px 0 0; padding: 0; list-style: none; }
.stats li { background: var(--surface); border-radius: 10px; padding: 10px 12px; font-size: 13px; color: var(--muted); }
.stats b { display: block; font-size: 19px; color: var(--text); font-variant-numeric: tabular-nums; }
.alert { margin: 12px 0 0; padding: 10px 12px; border-radius: 10px; background: var(--warn-soft); color: var(--warn); font-size: 14px; }
.alert[hidden] { display: none; }
.syringe { margin-top: 14px; }
.syringe svg { width: 100%; height: auto; }
.syringe .barrel { fill: var(--surface); stroke: var(--muted); }
.syringe .fill { fill: var(--accent); opacity: .75; }
.syringe .tick { stroke: var(--muted); }
.syringe .tick-label { fill: var(--muted); font-size: 9px; font-family: inherit; }
.syringe .plunger { fill: var(--muted); }

/* article */
.content { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 8px 28px 28px; margin: 24px 0; }
@media (max-width: 640px) { .content { padding: 4px 16px 20px; } }
.content h2 { font-size: 26px; line-height: 1.25; margin: 34px 0 10px; }
.content h3 { font-size: 19px; margin: 24px 0 6px; }
.content p, .content li { max-width: 760px; }
.content figure { margin: 22px 0; }
.content figcaption { font-size: 14px; color: var(--muted); margin-top: 8px; }
.formula { background: var(--surface-2); border-left: 4px solid var(--accent); border-radius: 8px; padding: 12px 16px; font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: 15px; overflow-x: auto; }
.table-wrap { overflow-x: auto; margin: 14px 0; }
table { border-collapse: collapse; width: 100%; font-size: 15px; font-variant-numeric: tabular-nums; }
th, td { text-align: left; padding: 9px 12px; border-bottom: 1px solid var(--border); white-space: nowrap; }
th { background: var(--surface-2); font-weight: 600; }
.tool table { font-size: 14px; }
.cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(230px, 1fr)); gap: 14px; margin: 14px 0; }
.card { border: 1px solid var(--border); border-radius: 12px; padding: 16px; background: var(--surface-2); }
.card h3 { margin-top: 0; font-size: 17px; }
.card p { margin: 6px 0 0; font-size: 15px; }
.note { font-size: 14px; color: var(--muted); border-top: 1px solid var(--border); padding-top: 14px; margin-top: 28px; }

/* footer */
.site-footer { border-top: 1px solid var(--border); background: var(--surface); padding: 24px 0 32px; font-size: 14px; color: var(--muted); }
.site-footer nav { display: flex; flex-wrap: wrap; gap: 6px 18px; margin-bottom: 10px; }
.site-footer a { color: var(--muted); }