:root {
  --primary: #f59e0b;
  --primary-dark: #d97706;
  --primary-light: #fde68a;
  --bg: #0f172a;
  --bg-card: #1e293b;
  --bg-card-hover: #243047;
  --border: #334155;
  --text: #f1f5f9;
  --text-muted: #94a3b8;
  --text-dim: #64748b;
  --pass: #22c55e;
  --warn: #f59e0b;
  --fail: #ef4444;
  --info: #38bdf8;
  --radius: 10px;
  --shadow: 0 4px 24px rgba(0,0,0,0.4);
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.6;
}

/* ── Header ─────────────────────────────────────────── */
header {
  background: linear-gradient(135deg, #1e293b 0%, #0f172a 100%);
  border-bottom: 1px solid var(--border);
  padding: 1.5rem 2rem;
  display: flex;
  align-items: center;
  gap: 1rem;
}

header .logo {
  font-size: 2rem;
  line-height: 1;
}

header h1 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--primary);
  letter-spacing: -0.02em;
}

header p {
  font-size: 0.875rem;
  color: var(--text-muted);
}

/* ── Layout ─────────────────────────────────────────── */
main {
  max-width: 1100px;
  margin: 0 auto;
  padding: 2rem 1.5rem 4rem;
  display: grid;
  gap: 1.5rem;
}

/* ── Cards ─────────────────────────────────────────── */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  box-shadow: var(--shadow);
}

.card-title {
  font-size: 1rem;
  font-weight: 700;
  color: var(--primary);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 1.25rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.card-title .icon {
  font-size: 1.1rem;
}

/* ── Form grid ─────────────────────────────────────── */
.form-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 1rem;
}

.field {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

label {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

label .unit {
  font-weight: 400;
  color: var(--text-dim);
  text-transform: none;
  letter-spacing: 0;
}

input[type="number"], input[type="text"] {
  background: #0f172a;
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--text);
  padding: 0.5rem 0.75rem;
  font-size: 0.95rem;
  width: 100%;
  transition: border-color 0.2s, box-shadow 0.2s;
  -moz-appearance: textfield;
}

input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button { opacity: 0.5; }

input[type="number"]:focus, input[type="text"]:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(245,158,11,0.2);
}

input.invalid {
  border-color: var(--fail) !important;
}

.field-hint {
  font-size: 0.72rem;
  color: var(--text-dim);
}

/* ── Action row ────────────────────────────────────── */
.action-row {
  display: flex;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
}

button#calculate {
  background: var(--primary);
  color: #0f172a;
  border: none;
  border-radius: 8px;
  padding: 0.75rem 2rem;
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  letter-spacing: 0.02em;
  transition: background 0.2s, transform 0.1s;
}

button#calculate:hover { background: var(--primary-dark); }
button#calculate:active { transform: scale(0.98); }

button#reset {
  background: transparent;
  color: var(--text-muted);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.75rem 1.5rem;
  font-size: 0.9rem;
  cursor: pointer;
  transition: border-color 0.2s, color 0.2s;
}
button#reset:hover { border-color: var(--text-muted); color: var(--text); }

#validation-msg {
  color: var(--fail);
  font-size: 0.875rem;
}

/* ── Results ───────────────────────────────────────── */
#results {
  display: none;
}

#results.visible {
  display: block;
}

.results-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.stat-card {
  background: #0f172a;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1rem 1.25rem;
}

.stat-label {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.25rem;
}

.stat-value {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text);
  line-height: 1.2;
}

.stat-unit {
  font-size: 0.9rem;
  color: var(--text-muted);
  font-weight: 400;
}

.stat-note {
  font-size: 0.75rem;
  color: var(--text-dim);
  margin-top: 0.25rem;
}

/* ── Safety checks ─────────────────────────────────── */
.checks-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.875rem;
}

.checks-table th {
  text-align: left;
  padding: 0.5rem 1rem;
  color: var(--text-muted);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  border-bottom: 1px solid var(--border);
}

.checks-table td {
  padding: 0.65rem 1rem;
  border-bottom: 1px solid rgba(51,65,85,0.5);
}

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

.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  padding: 0.2rem 0.6rem;
  border-radius: 20px;
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.badge-pass { background: rgba(34,197,94,0.15); color: var(--pass); }
.badge-warn { background: rgba(245,158,11,0.15); color: var(--warn); }
.badge-fail { background: rgba(239,68,68,0.15); color: var(--fail); }

/* ── Summary banner ────────────────────────────────── */
#summary-banner {
  padding: 1rem 1.5rem;
  border-radius: 8px;
  font-size: 0.9rem;
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-top: 1.5rem;
}

#summary-banner.pass { background: rgba(34,197,94,0.1); border: 1px solid rgba(34,197,94,0.3); color: var(--pass); }
#summary-banner.warn { background: rgba(245,158,11,0.1); border: 1px solid rgba(245,158,11,0.3); color: var(--warn); }
#summary-banner.fail { background: rgba(239,68,68,0.1); border: 1px solid rgba(239,68,68,0.3); color: var(--fail); }

/* ── Section dividers ──────────────────────────────── */
.section-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
}

@media (max-width: 720px) {
  .section-row { grid-template-columns: 1fr; }
  header { flex-direction: column; align-items: flex-start; gap: 0.25rem; }
}

/* ── Tooltip ───────────────────────────────────────── */
.help {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 1rem;
  height: 1rem;
  border-radius: 50%;
  background: var(--border);
  color: var(--text-muted);
  font-size: 0.65rem;
  font-weight: 700;
  cursor: help;
  margin-left: 0.3rem;
  position: relative;
  vertical-align: middle;
}

.help::after {
  content: attr(data-tip);
  position: absolute;
  bottom: calc(100% + 6px);
  left: 50%;
  transform: translateX(-50%);
  background: #334155;
  color: var(--text);
  font-size: 0.75rem;
  font-weight: 400;
  text-transform: none;
  letter-spacing: 0;
  padding: 0.4rem 0.65rem;
  border-radius: 6px;
  white-space: normal;
  pointer-events: none;
  opacity: 0;
  transition: opacity 0.15s;
  z-index: 10;
  box-shadow: 0 4px 12px rgba(0,0,0,0.4);
  min-width: 160px;
  text-align: center;
  max-width: 220px;
}

.help:hover::after { opacity: 1; }