:root {
  --bg: #f5f6f1;
  --surface: #ffffff;
  --text: #1c2321;
  --muted: #566660;
  --line: #dfe4dc;
  --accent: #0b6b5d;
  --accent-ink: #ffffff;
  --accent-soft: #e3f1ec;
  --danger: #b3261e;
  --danger-soft: #fbe9e7;
  --focus: #1d4ed8;
  --radius: 14px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #111716;
    --surface: #1a2220;
    --text: #e8eeeb;
    --muted: #9fb0aa;
    --line: #2b3733;
    --accent: #4cc3ad;
    --accent-ink: #06201b;
    --accent-soft: #1d3a34;
    --danger: #ff8a80;
    --danger-soft: #3a1f1c;
    --focus: #8ab4ff;
  }
}

*, *::before, *::after { 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, Arial, sans-serif;
}

a { color: var(--accent); text-underline-offset: 2px; }
a:hover { text-decoration-thickness: 2px; }
:focus-visible { outline: 3px solid var(--focus); outline-offset: 2px; border-radius: 4px; }

.skip-link {
  position: absolute; left: -999px; top: 8px;
  background: var(--accent); color: var(--accent-ink);
  padding: 8px 12px; border-radius: 8px; z-index: 10;
}
.skip-link:focus { left: 8px; }

.wrap { max-width: 760px; margin: 0 auto; padding: 0 16px; }

/* ---------- header ---------- */
.site-header { background: var(--surface); border-bottom: 1px solid var(--line); }
.site-header .wrap { padding-top: 14px; padding-bottom: 14px; }
.brand {
  display: inline-block; font-weight: 800; font-size: 1.3rem; letter-spacing: -0.02em;
  color: var(--text); text-decoration: none;
}
.brand span { color: var(--accent); }
.nav { margin: 10px 0 0; padding: 0; list-style: none; display: flex; flex-wrap: wrap; gap: 6px; }
.nav a {
  display: flex; align-items: center; min-height: 44px; padding: 6px 14px; border-radius: 999px;
  font-size: 0.92rem; font-weight: 600; text-decoration: none; color: var(--muted);
  border: 1px solid var(--line);
}
.nav a:hover { color: var(--text); border-color: var(--accent); }
.nav a[aria-current="page"] { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }

/* ---------- typography ---------- */
main { padding: 28px 0 48px; }
h1 { font-size: clamp(1.7rem, 5.5vw, 2.3rem); line-height: 1.2; letter-spacing: -0.02em; margin: 0 0 12px; }
h2 { font-size: 1.35rem; line-height: 1.3; margin: 40px 0 10px; letter-spacing: -0.01em; }
h3 { font-size: 1.1rem; margin: 22px 0 6px; }
p { margin: 0 0 14px; }
ul, ol { padding-left: 1.3em; margin: 0 0 14px; }
li { margin-bottom: 6px; }
.lead { font-size: 1.1rem; color: var(--muted); }
.note { font-size: 0.9rem; color: var(--muted); }

.formula {
  background: var(--accent-soft); border-left: 4px solid var(--accent);
  padding: 10px 14px; margin: 0 0 12px; border-radius: 0 10px 10px 0;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: 0.95rem;
  overflow-x: auto;
}

/* ---------- calculator cards ---------- */
.card {
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 20px 16px; margin: 0 0 18px;
}
.card h2, .card h3 { margin-top: 0; }
.card .hint { color: var(--muted); font-size: 0.92rem; margin-bottom: 14px; }

.fields { display: grid; gap: 14px; grid-template-columns: repeat(auto-fit, minmax(190px, 1fr)); }
label { display: block; font-weight: 600; font-size: 0.95rem; margin-bottom: 5px; }
label .opt { font-weight: 400; color: var(--muted); }
input[type="text"], input[type="email"], textarea {
  width: 100%; min-height: 48px; padding: 10px 12px;
  font: inherit; font-size: 16px; /* 16px stops iOS zooming into the field */
  color: var(--text); background: var(--bg);
  border: 1.5px solid var(--line); border-radius: 10px;
}
textarea { min-height: 140px; resize: vertical; }
input[aria-invalid="true"] { border-color: var(--danger); background: var(--danger-soft); }

.actions { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 16px; }
.btn {
  flex: 1 1 140px; min-height: 48px; padding: 10px 18px;
  font: inherit; font-weight: 700; cursor: pointer;
  border-radius: 10px; border: 1.5px solid var(--accent);
  background: var(--accent); color: var(--accent-ink);
}
.btn:hover { filter: brightness(1.07); }
.btn-ghost { background: transparent; color: var(--accent); }
.btn-ghost:hover { background: var(--accent-soft); filter: none; }

.error {
  margin: 14px 0 0; padding: 10px 12px; border-radius: 10px;
  background: var(--danger-soft); color: var(--danger); font-weight: 600; font-size: 0.95rem;
}
.result {
  margin-top: 16px; padding: 16px; border-radius: 12px;
  background: var(--accent-soft); border: 1px solid var(--accent);
}
.result[hidden], .error[hidden] { display: none; }
.result .answer-label { margin: 0; font-size: 0.9rem; color: var(--muted); font-weight: 600; }
.result .answer { margin: 2px 0 6px; font-size: 2.1rem; font-weight: 800; line-height: 1.15; overflow-wrap: anywhere; }
.result .sentence { margin: 0 0 8px; }
.result dl { margin: 8px 0 0; display: grid; grid-template-columns: 1fr auto; gap: 4px 12px; font-size: 0.97rem; }
.result dt { color: var(--muted); }
.result dd { margin: 0; font-weight: 700; text-align: right; overflow-wrap: anywhere; }

/* ---------- content blocks ---------- */
.table-scroll { overflow-x: auto; margin: 0 0 14px; }
table { border-collapse: collapse; width: 100%; min-width: 440px; font-size: 0.95rem; }
th, td { text-align: left; padding: 8px 10px; border-bottom: 1px solid var(--line); vertical-align: top; }
th { background: var(--accent-soft); }

details { background: var(--surface); border: 1px solid var(--line); border-radius: 10px; padding: 0 14px; margin-bottom: 8px; }
summary { cursor: pointer; font-weight: 700; padding: 12px 0; }
details[open] summary { margin-bottom: 4px; }

.cards { display: grid; gap: 14px; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); margin: 20px 0 8px; }
.tile {
  display: block; text-decoration: none; color: var(--text);
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 18px 16px;
}
.tile:hover { border-color: var(--accent); }
.tile strong { display: block; font-size: 1.1rem; color: var(--accent); margin-bottom: 4px; }
.tile span { color: var(--muted); font-size: 0.95rem; }

.related { display: flex; flex-wrap: wrap; gap: 8px; padding: 0; list-style: none; }
.related a {
  display: flex; align-items: center; min-height: 44px; padding: 8px 16px; border: 1px solid var(--line); border-radius: 999px;
  background: var(--surface); text-decoration: none; font-weight: 600;
}
.related a:hover { border-color: var(--accent); }

.disclaimer { font-size: 0.88rem; color: var(--muted); border-top: 1px solid var(--line); padding-top: 14px; margin-top: 36px; }

/* ---------- creator ---------- */
.creator-band { padding: 0 0 28px; }
.creator { display: flex; align-items: center; gap: 14px; }
.creator-photo {
  flex: none; display: block; width: 72px; height: 72px; padding: 3px; border-radius: 50%;
  background: conic-gradient(var(--accent) 0 40%, #f2b01e 40% 70%, #e0524a 70% 85%, var(--accent) 85% 100%);
}
.creator-photo img {
  display: block; width: 100%; height: 100%; border-radius: 50%; object-fit: cover;
  background: var(--accent-soft); border: 2px solid var(--surface);
}
.creator-text p { margin: 0; line-height: 1.35; }
.creator-label { font-size: 0.8rem; font-weight: 700; letter-spacing: 0.04em; text-transform: uppercase; color: var(--muted); }
.creator-name { font-size: 1.05rem; font-weight: 700; }
.creator-name a { color: var(--text); }
.creator-role { font-size: 0.92rem; color: var(--muted); }
.creator-large { margin: 0 0 16px; }
.creator-large .creator-photo { width: 108px; height: 108px; padding: 4px; }

/* ---------- footer ---------- */
.site-footer { border-top: 1px solid var(--line); background: var(--surface); padding: 22px 0 30px; font-size: 0.92rem; color: var(--muted); }
.site-footer ul { list-style: none; padding: 0; margin: 0 0 10px; display: flex; flex-wrap: wrap; gap: 6px 18px; }
.site-footer a { color: var(--muted); }
.site-footer p { margin: 0; }

@media (min-width: 600px) {
  .card { padding: 24px 22px; }
  .btn { flex: 0 1 auto; min-width: 150px; }
}
@media print {
  .site-header, .site-footer, .actions { display: none; }
}