:root {
  --water-ink: #183a3b;
  --water-muted: #5b7473;
  --water-line: #cbdcda;
  --water-panel: #f7fbfa;
  --water-accent: #146f69;
  --water-accent-dark: #0d524e;
  --water-soft: #e7f3f0;
  --water-warn: #8b5b17;
  --water-danger: #9a3329;
}

* { box-sizing: border-box; }
body { color: var(--water-ink); }
.intro { margin-bottom: 22px; }
.intro h1 { font-size: clamp(1.8rem, 3vw, 2.6rem); line-height: 1.2; margin: 8px 0 10px; }
.eyebrow, .section-kicker { color: var(--water-accent); font-size: .78rem; font-weight: 700; letter-spacing: .12em; margin: 0; text-transform: uppercase; }
.lead { line-height: 1.8; margin: 0; max-width: 780px; }
.tool-shell { border: 1px solid var(--water-line); display: grid; grid-template-columns: minmax(0, 1.08fr) minmax(300px, .92fr); margin-top: 20px; }
.calculator-panel, .info-panel { min-width: 0; padding: clamp(18px, 3vw, 28px); }
.calculator-panel { border-right: 1px solid var(--water-line); }
.section-heading h2 { font-size: 1.45rem; line-height: 1.35; margin: 8px 0 20px; }
.input-grid { display: grid; gap: 16px; grid-template-columns: repeat(2, minmax(0, 1fr)); }
.field { display: grid; gap: 7px; font-weight: 700; min-width: 0; }
.field-wide { grid-column: 1 / -1; }
.field input, .field select { background: #fff; border: 1px solid #8ba6a3; border-radius: 4px; color: var(--water-ink); font: inherit; min-height: 46px; padding: 10px 11px; width: 100%; }
.field input:focus-visible, .field select:focus-visible, .button:focus-visible, a:focus-visible { border-color: var(--water-accent); outline: 3px solid rgba(20, 111, 105, .25); outline-offset: 2px; }
.field input[aria-invalid="true"], .field select[aria-invalid="true"] { border-color: var(--water-danger); box-shadow: 0 0 0 2px rgba(154, 51, 41, .12); }
.field small { color: var(--water-muted); font-size: .82rem; font-weight: 400; line-height: 1.55; }
.optional { color: var(--water-muted); font-size: .82em; font-weight: 400; }
.unit-input { display: grid; grid-template-columns: minmax(0, 1fr) auto; }
.unit-suffix { align-items: center; background: var(--water-soft); border: 1px solid #8ba6a3; border-left: 0; display: inline-flex; min-width: 62px; justify-content: center; padding: 0 10px; }
.form-error { background: #fff2ef; border-left: 4px solid var(--water-danger); color: #7f2b24; font-weight: 700; line-height: 1.6; margin: 16px 0 0; padding: 11px 13px; }
.form-actions { align-items: center; border-top: 1px solid var(--water-line); display: flex; flex-wrap: wrap; gap: 8px; margin-top: 20px; padding-top: 20px; }
.button { border: 1px solid var(--water-accent); border-radius: 4px; cursor: pointer; font: inherit; font-weight: 700; min-height: 46px; padding: 10px 16px; }
.button-primary { background: var(--water-accent); color: #fff; }
.button-primary:hover { background: var(--water-accent-dark); }
.button-secondary { background: #fff; color: var(--water-accent-dark); }
.button-secondary:hover { background: var(--water-soft); }
.result-box { border: 1px solid var(--water-accent); margin-top: 18px; padding: 18px; }
.result-box[data-state="waiting"] { border-color: #9aaba9; }
.result-box[data-state="error"] { border-color: var(--water-danger); }
.result-label { color: var(--water-muted); font-size: .82rem; margin: 0; }
.result-status { color: #4d6260; line-height: 1.65; margin: 7px 0 0; }
.output-groups { display: grid; gap: 12px; grid-template-columns: repeat(2, minmax(0, 1fr)); margin-top: 18px; }
.output-group { background: #fff; border: 1px solid var(--water-line); min-width: 0; padding: 14px; }
.output-group h3 { font-size: 1rem; margin: 0 0 10px; }
.output-list { display: grid; gap: 6px; margin: 0; }
.output-list div { align-items: baseline; border-bottom: 1px solid #e4eceb; display: flex; gap: 10px; justify-content: space-between; padding: 5px 0; }
.output-list dt { color: var(--water-muted); font-size: .85rem; }
.output-list dd { font-variant-numeric: tabular-nums; margin: 0; overflow-wrap: anywhere; text-align: right; }
.result-details { display: grid; gap: 0; grid-template-columns: repeat(2, minmax(0, 1fr)); margin: 18px 0 0; }
.result-details div { border: 1px solid var(--water-line); margin: -1px 0 0 -1px; min-width: 0; padding: 10px; }
.result-details .detail-wide { grid-column: 1 / -1; }
.result-details dt { color: var(--water-muted); font-size: .78rem; margin-bottom: 4px; }
.result-details dd { line-height: 1.6; margin: 0; overflow-wrap: anywhere; }
.info-panel { background: var(--water-panel); }
.formula-card { background: #fff; border: 1px solid var(--water-line); display: grid; gap: 8px; margin-top: 12px; padding: 16px; }
.formula-card strong { font-size: clamp(1.05rem, 2vw, 1.25rem); overflow-wrap: anywhere; }
.formula-card span, .info-note { color: var(--water-muted); line-height: 1.7; }
.info-note { border-left: 4px solid var(--water-accent); margin: 16px 0 0; padding-left: 12px; }
.content-section { margin-top: 48px; }
.method-grid { display: grid; gap: 0; grid-template-columns: repeat(2, minmax(0, 1fr)); }
.method-grid article { border: 1px solid var(--water-line); display: grid; gap: 8px; margin: -1px 0 0 -1px; min-width: 0; padding: 18px; }
.method-grid strong { font-size: 1rem; overflow-wrap: anywhere; }
.method-grid span { color: var(--water-muted); font-size: .87rem; line-height: 1.65; }
.proof-guide { border: 1px solid var(--water-line); margin-top: 20px; padding: 20px; }
.proof-guide h3 { margin: 0 0 10px; }
.proof-guide ul { margin: 0; padding-left: 22px; }
.proof-guide li { line-height: 1.8; }
.sources ul { display: grid; gap: 8px; margin: 0; padding-left: 22px; }
.sources li { line-height: 1.6; overflow-wrap: anywhere; }
.sources a { color: var(--water-accent-dark); }
.site-footer .footer-inner { align-items: center; display: flex; flex-wrap: wrap; gap: 14px; }
.site-footer a { color: inherit; }

@media (max-width: 900px) {
  .tool-shell { grid-template-columns: 1fr; }
  .calculator-panel { border-bottom: 1px solid var(--water-line); border-right: 0; }
}

@media (max-width: 620px) {
  .calculator-panel, .info-panel { padding: 20px 14px; }
  .input-grid, .output-groups, .method-grid { grid-template-columns: 1fr; }
  .field-wide { grid-column: auto; }
  .result-details { grid-template-columns: 1fr; }
  .result-details .detail-wide { grid-column: auto; }
  .form-actions { display: grid; grid-template-columns: 1fr 1fr; }
  .form-actions .button-primary { grid-column: 1 / -1; }
  .button { padding-inline: 10px; width: 100%; }
  .site-footer .footer-inner { align-items: flex-start; flex-direction: column; }
}

@media (prefers-reduced-motion: reduce) {
  * { scroll-behavior: auto !important; transition-duration: .01ms !important; }
}