:root {
  --bg: #f7f9fa;
  --surface: #ffffff;
  --surface-alt: #f0f4f7;
  --border: #dce3e8;
  --border-strong: #bcc8d1;
  --text: #142634;
  --text-muted: #4a5d6e;
  --accent: #0c6e87;
  --accent-dark: #085063;
  --accent-soft: #e6f4f7;
  --ok-text: #14532d;
  --ok-bg: #ecfdf5;
  --ok-border: #86efac;
  --warn-text: #92400e;
  --warn-bg: #fffbeb;
  --warn-border: #fcd34d;
  --bad-text: #991b1b;
  --bad-bg: #fef2f2;
  --bad-border: #fca5a5;
  --radius: 10px;
  --max-w: 1120px;
  --header-h: 64px;
}

*, *::before, *::after {
  box-sizing: border-box;
}

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

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition: none !important; animation: none !important; }
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.62;
  font-size: 16px;
}

.num, .tabular {
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-variant-numeric: tabular-nums;
}

a {
  color: var(--accent-dark);
  text-decoration-thickness: 1.5px;
  text-underline-offset: 2px;
}

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

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--accent-dark);
  color: #fff;
  padding: 8px 14px;
  z-index: 200;
}
.skip-link:focus {
  left: 8px;
  top: 8px;
}

.container {
  width: 100%;
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 20px;
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.96);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: var(--header-h);
  gap: 16px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: var(--text);
  font-weight: 700;
  font-size: 1.05rem;
  letter-spacing: -0.01em;
  flex-shrink: 0;
}

.brand-mark {
  width: 28px;
  height: 28px;
  border-radius: 7px;
  background: var(--accent);
  color: #fff;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 0.8rem;
  font-weight: 800;
}

.nav-toggle {
  display: none;
  background: var(--surface);
  border: 1px solid var(--border-strong);
  border-radius: 8px;
  padding: 6px 12px;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text);
  cursor: pointer;
}

.site-nav {
  display: flex;
  align-items: center;
  gap: 6px;
  flex-wrap: wrap;
}

.site-nav a {
  text-decoration: none;
  color: var(--text-muted);
  font-size: 0.92rem;
  font-weight: 500;
  padding: 6px 10px;
  border-radius: 7px;
  white-space: nowrap;
}

.site-nav a:hover {
  background: var(--surface-alt);
  color: var(--text);
}

.site-nav a[aria-current="page"] {
  background: var(--accent-soft);
  color: var(--accent-dark);
  font-weight: 600;
}

@media (max-width: 860px) {
  .nav-toggle { display: inline-flex; align-items: center; gap: 6px; }
  .site-nav {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    padding: 12px 20px 16px;
    flex-direction: column;
    align-items: stretch;
    box-shadow: 0 8px 20px rgba(20, 38, 52, 0.08);
  }
  .site-nav.open { display: flex; }
  .site-nav a { padding: 10px 12px; }
}

/* Main & Sections */
main {
  padding: 28px 0 56px;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.05fr 0.95fr;
  gap: 28px;
  align-items: start;
  margin-bottom: 36px;
}

@media (max-width: 860px) {
  .hero-grid {
    grid-template-columns: 1fr;
    gap: 20px;
  }
}

.eyebrow {
  display: inline-block;
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--accent-dark);
  background: var(--accent-soft);
  padding: 3px 9px;
  border-radius: 5px;
  margin-bottom: 10px;
}

h1 {
  margin: 0 0 12px;
  font-size: clamp(1.7rem, 3vw, 2.3rem);
  line-height: 1.2;
  letter-spacing: -0.02em;
}

h2 {
  margin: 34px 0 12px;
  font-size: clamp(1.3rem, 2.2vw, 1.6rem);
  line-height: 1.28;
  letter-spacing: -0.01em;
}

h3 {
  margin: 20px 0 8px;
  font-size: 1.1rem;
  line-height: 1.35;
}

p {
  margin: 0 0 14px;
}

.lead {
  font-size: 1.06rem;
  color: var(--text-muted);
  margin-bottom: 18px;
}

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px;
  box-shadow: 0 1px 3px rgba(20, 38, 52, 0.04);
}

.card-title {
  margin: 0 0 14px;
  font-size: 1.12rem;
  font-weight: 700;
}

/* Form Controls */
.form-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
}

@media (max-width: 540px) {
  .form-grid { grid-template-columns: 1fr; }
}

.field {
  display: flex;
  flex-direction: column;
  gap: 5px;
  margin-bottom: 14px;
}

.field label {
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--text);
}

.input-wrap {
  position: relative;
  display: flex;
  align-items: center;
}

.field input, .field select {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--border-strong);
  border-radius: 7px;
  font-size: 0.98rem;
  color: var(--text);
  background: var(--surface);
}

.field input.has-unit {
  padding-right: 54px;
}

.unit-tag {
  position: absolute;
  right: 12px;
  font-size: 0.82rem;
  color: var(--text-muted);
  pointer-events: none;
}

.field input:focus, .field select:focus {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
  border-color: var(--accent);
}

.btn-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 6px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 10px 16px;
  border-radius: 7px;
  font-size: 0.94rem;
  font-weight: 600;
  cursor: pointer;
  border: 1px solid transparent;
  text-decoration: none;
}

.btn-primary {
  background: var(--accent);
  color: #fff;
}
.btn-primary:hover { background: var(--accent-dark); }

.btn-secondary {
  background: var(--surface-alt);
  color: var(--text);
  border-color: var(--border-strong);
}
.btn-secondary:hover { background: var(--border); }

/* Result Boxes */
.result-box {
  margin-top: 18px;
  padding: 16px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--surface-alt);
}

.result-box.status-healthy { background: var(--ok-bg); border-color: var(--ok-border); color: var(--ok-text); }
.result-box.status-borderline,
.result-box.status-tds_creep_caution,
.result-box.status-remineralized_caution,
.result-box.status-retest_anomaly { background: var(--warn-bg); border-color: var(--warn-border); color: var(--warn-text); }
.result-box.status-action_needed,
.result-box.status-error { background: var(--bad-bg); border-color: var(--bad-border); color: var(--bad-text); }

.result-headline {
  font-size: 1.08rem;
  font-weight: 700;
  margin: 0 0 6px;
}

.result-box ul {
  margin: 10px 0 0;
  padding-left: 20px;
}

.result-box li {
  margin-bottom: 5px;
}

/* Diagrams / Figures */
.diagram-figure {
  margin: 24px 0;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px;
}

.diagram-figure svg {
  display: block;
  width: 100%;
  height: auto;
  max-width: 100%;
}

.diagram-caption {
  margin-top: 12px;
  font-size: 0.88rem;
  color: var(--text-muted);
  border-top: 1px solid var(--border);
  padding-top: 10px;
}

/* Tables & Grids */
.table-wrap {
  width: 100%;
  overflow-x: auto;
  margin: 16px 0 24px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.94rem;
}

th, td {
  padding: 11px 14px;
  text-align: left;
  border-bottom: 1px solid var(--border);
}

th {
  background: var(--surface-alt);
  font-weight: 600;
}

tr:last-child td { border-bottom: none; }

.two-col {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 20px;
  margin: 18px 0;
}

@media (max-width: 720px) {
  .two-col { grid-template-columns: 1fr; }
}

.callout {
  border-left: 4px solid var(--accent);
  background: var(--surface);
  border-top: 1px solid var(--border);
  border-right: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
  border-radius: 0 var(--radius) var(--radius) 0;
  padding: 14px 18px;
  margin: 18px 0;
}

.meta-note {
  font-size: 0.86rem;
  color: var(--text-muted);
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--border);
  background: var(--surface);
  padding: 28px 0;
  font-size: 0.9rem;
  color: var(--text-muted);
}

.footer-grid {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 20px;
}

.footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
}

@media print {
  .site-header, .nav-toggle, .btn-row { display: none !important; }
  body { background: #fff; }
  .card { box-shadow: none; }
}