/* ── Design tokens — Units & Measures / amber-brass theme ── */
:root {
  --bg: #0c0d0f;
  --panel: #111214;
  --panel2: #15171a;
  --text: #f5f6f7;
  --dim: #9aa3b2;
  --muted: #6b7280;
  --border: #2a2a2a;
  --line: #1e1e1e;
  --accent: #fbbf24;
  --accent2: #fcd34d;
  --shadow: rgba(0, 0, 0, 0.35);
  --good: #34d399;
  --bad: #fb7185;
  --mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono",
    "Courier New", monospace;
  --sans: Inter, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    "Helvetica Neue", Arial, "Noto Sans", sans-serif;
  --brass: #d97706;
  --cool: #67e8f9;
  --warm: #fbbf24;
}

html, body { min-height: 100%; }
html { scrollbar-gutter: stable both-edges; overflow-y: scroll; }

body {
  margin: 0; min-height: 100dvh;
  background: var(--bg); color: var(--text);
  font-family: var(--sans); line-height: 1.45;
  overflow-x: hidden;
}

a { color: var(--accent); text-decoration: none; }
a:hover { color: var(--accent2); }

.wrap { max-width: 1100px; margin: 0 auto; padding: 18px 18px 54px; }

.skip-link {
  position: absolute; left: 12px; top: 10px;
  padding: 0.5rem 0.7rem; border-radius: 0.3rem;
  border: 2px solid var(--border); background: var(--panel); color: var(--text);
  transform: translateY(-140%); transition: transform 0.15s ease; z-index: 20000;
}
.skip-link:focus { transform: translateY(0); }

/* ── Header ── */
.site-header { display: flex; flex-direction: column; gap: 0.65rem; padding-top: calc(3.2rem + env(safe-area-inset-top, 0px)); }
.topbar {
  position: fixed; top: 0; left: 0; right: 0; z-index: 9000; padding-top: env(safe-area-inset-top, 0px);
  background: rgba(12, 13, 15, 0.85); backdrop-filter: blur(10px);
  border-bottom: 2px solid var(--border);
}
.topbar-content {
  max-width: 1100px; margin: 0 auto;
  display: flex; align-items: center; justify-content: space-between;
  padding: 0.55rem 18px; gap: 1rem;
}
.brand { font-family: var(--mono); font-size: 1.1rem; font-weight: 800; color: var(--accent); white-space: nowrap; }

/* ── Intro ── */
.intro { margin-bottom: 1.5rem; }
.intro-title { font-size: 1.6rem; font-weight: 800; margin: 0 0 0.4rem; color: var(--text); }
.intro-subtitle { font-size: 0.95rem; color: var(--dim); margin: 0; max-width: 640px; line-height: 1.5; }

/* ── Sections ── */
.section-card {
  background: var(--panel); border: 2px solid var(--border);
  border-radius: 0.35rem; padding: 1.25rem 1.5rem; margin-bottom: 1.25rem;
}
.section-heading { font-size: 1.15rem; font-weight: 650; margin: 0 0 0.3rem; color: var(--accent); }
.section-desc { font-size: 0.88rem; color: var(--dim); margin: 0 0 1rem; line-height: 1.55; }
.section-desc strong { color: var(--text); font-weight: 600; }

/* ── Hero ── */
.hero-card { text-align: center; padding: 1.5rem 1.5rem; }
.hero-label {
  font-size: 0.75rem; font-weight: 600; color: var(--muted);
  text-transform: uppercase; letter-spacing: 0.08em; margin-bottom: 1rem;
}
.hero-lab { display: flex; flex-direction: column; gap: 1rem; }
.hero-canvas {
  width: 100%; height: 480px;
  background: #0a0906; border: 2px solid var(--border);
  border-radius: 0.3rem; display: block;
}
.hero-controls {
  display: flex; gap: 1.5rem; flex-wrap: wrap;
  justify-content: center; align-items: flex-start; max-width: 700px; margin: 0 auto;
}
.hero-controls .control-group { min-width: 200px; }
.hero-readouts {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(130px, 1fr));
  gap: 0.5rem; width: 100%;
}
.readout {
  background: var(--panel2); border: 2px solid var(--border);
  border-radius: 0.3rem; padding: 0.5rem 0.7rem; text-align: center;
}
.readout-label { display: block; font-size: 0.75rem; font-weight: 600; color: var(--muted); text-transform: uppercase; letter-spacing: 0.06em; margin-bottom: 0.15rem; }
.readout-value { display: block; font-size: 0.92rem; font-weight: 700; color: var(--accent); font-family: var(--mono); }

/* ── Gallery ── */
.filter-chips { display: flex; flex-wrap: wrap; gap: 0.4rem; margin-bottom: 1rem; }
.filter-chip {
  font-size: 0.78rem; font-weight: 600;
  padding: 0.3rem 0.7rem; border-radius: 999px;
  background: var(--panel2); border: 2px solid var(--border);
  color: var(--dim); cursor: pointer; font-family: var(--sans);
  transition: color 0.15s, border-color 0.15s;
}
.filter-chip:hover { color: var(--text); border-color: var(--accent); }
.filter-chip.active {
  color: var(--accent); border-color: var(--accent);
  background: rgba(251, 191, 36, 0.08);
}
.gallery-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 0.75rem; }
.gallery-empty { text-align: center; padding: 2rem; color: var(--muted); font-size: 0.88rem; }
.gallery-empty[hidden] { display: none; }
.artifact-card {
  background: var(--panel2); border: 2px solid var(--border);
  border-radius: 0.3rem; padding: 1rem;
  cursor: pointer; transition: border-color 0.25s;
  display: flex; flex-direction: column; gap: 0.5rem; min-height: 120px;
}
.artifact-card:hover { border-color: var(--accent); }
.artifact-card:active { background: rgba(251, 191, 36, 0.04); }
.artifact-title { font-size: 0.95rem; font-weight: 650; color: var(--text); margin: 0 0 0.15rem; }
.artifact-year { font-size: 0.75rem; font-weight: 600; color: var(--muted); font-family: var(--mono); }
.artifact-desc { font-size: 0.8rem; color: var(--dim); line-height: 1.5; margin: 0; flex: 1; }
.artifact-funfact {
  font-size: 0.75rem; color: var(--muted); line-height: 1.45;
  margin: 0; padding-top: 0.35rem;
  border-top: 1px solid var(--line);
}
.artifact-meta { display: flex; align-items: center; gap: 0.5rem; flex-wrap: wrap; }

/* ── Timeline ── */
.timeline-strip {
  display: flex; gap: 1rem; overflow-x: auto;
  scroll-snap-type: x mandatory; padding: 0.5rem 0 1rem;
  -webkit-overflow-scrolling: touch;
}
.timeline-strip::-webkit-scrollbar { height: 6px; }
.timeline-strip::-webkit-scrollbar-track { background: var(--panel2); border-radius: 3px; }
.timeline-strip::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }
.timeline-card {
  flex: 0 0 260px; scroll-snap-align: start;
  background: var(--panel2); border: 2px solid var(--border);
  border-radius: 0.3rem; padding: 1rem 1.1rem;
  transition: border-color 0.25s; cursor: pointer;
}
.timeline-card.active { border-color: var(--accent); }
.timeline-year { font-size: 1.3rem; font-weight: 800; color: var(--accent); font-family: var(--mono); margin: 0 0 0.2rem; }
.timeline-title { font-size: 0.92rem; font-weight: 650; color: var(--text); margin: 0 0 0.4rem; }
.timeline-blurb { font-size: 0.8rem; color: var(--dim); line-height: 1.5; margin: 0; }
.timeline-narrative {
  flex: 0 0 320px; cursor: default;
  background: linear-gradient(135deg, rgba(251, 191, 36, 0.06), rgba(251, 191, 36, 0.02));
  border-color: var(--accent); border-style: dashed;
}
.narrative-title {
  font-size: 0.85rem; font-weight: 700; color: var(--accent);
  text-transform: uppercase; letter-spacing: 0.06em; margin: 0 0 0.5rem;
}
.narrative-text {
  font-size: 0.78rem; color: var(--dim); line-height: 1.6; margin: 0;
  font-style: italic;
}

/* ── Playground ── */
.playground-tabs { display: flex; gap: 0.4rem; margin-bottom: 1rem; flex-wrap: wrap; }
.tab-btn {
  font-size: 0.78rem; font-weight: 600;
  padding: 0.4rem 0.85rem; border-radius: 0.3rem;
  background: var(--panel2); border: 2px solid var(--border);
  color: var(--dim); cursor: pointer; font-family: var(--sans);
  transition: color 0.15s, border-color 0.15s;
}
.tab-btn:hover { color: var(--text); border-color: var(--accent); }
.tab-btn.active {
  color: var(--accent); border-color: var(--accent);
  background: rgba(251, 191, 36, 0.08);
}
.tab-panel[hidden] { display: none; }

/* ── Unit Converter ── */
.converter-layout { display: flex; flex-direction: column; gap: 1rem; }
.converter-dimension-row, .converter-input-row { display: flex; gap: 1rem; flex-wrap: wrap; align-items: flex-end; }
.converter-input-row input, .converter-input-row select,
.converter-dimension-row select {
  padding: 0.5rem 0.7rem; border-radius: 0.3rem;
  background: var(--panel2); border: 2px solid var(--border);
  color: var(--text); font-family: var(--mono); font-size: 0.95rem; outline: none;
}
.converter-input-row input { width: 180px; }
.converter-input-row select, .converter-dimension-row select { font-family: var(--sans); font-size: 0.85rem; cursor: pointer; min-width: 200px; }
.converter-input-row input:focus, .converter-input-row select:focus,
.converter-dimension-row select:focus { border-color: var(--accent); }
.converter-results { display: grid; grid-template-columns: 1fr; gap: 0.35rem; }
.converter-row {
  display: grid; grid-template-columns: 180px 1fr;
  align-items: center; gap: 0.5rem; font-size: 0.82rem;
  padding: 0.4rem 0.6rem; background: var(--panel2); border-radius: 0.2rem;
}
.converter-row.highlight { border: 1px solid var(--accent); background: rgba(251, 191, 36, 0.05); }
.converter-label { font-weight: 600; color: var(--dim); }
.converter-value { font-family: var(--mono); color: var(--accent); word-break: break-all; }

/* ── Historical Units ── */
.historical-layout { display: flex; flex-direction: column; gap: 1rem; }
.historical-intro { font-size: 0.85rem; color: var(--dim); margin: 0; line-height: 1.55; }

/* ── SI Base Units grid ── */
.si-layout { display: flex; flex-direction: column; gap: 1rem; }
.si-intro { font-size: 0.85rem; color: var(--dim); margin: 0; line-height: 1.55; }
.si-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); gap: 0.75rem; }
.si-card {
  background: var(--panel2); border: 2px solid var(--border);
  border-radius: 0.3rem; padding: 1rem;
  display: flex; flex-direction: column; gap: 0.4rem;
  transition: border-color 0.25s;
}
.si-card:hover { border-color: var(--accent); }
.si-card-head { display: flex; justify-content: space-between; align-items: baseline; gap: 0.5rem; }
.si-card-symbol { font-size: 1.6rem; font-weight: 800; color: var(--accent); font-family: var(--mono); }
.si-card-name { font-size: 0.95rem; font-weight: 650; color: var(--text); }
.si-card-quantity { font-size: 0.75rem; color: var(--muted); text-transform: uppercase; letter-spacing: 0.06em; font-weight: 600; }
.si-card-def { font-size: 0.78rem; color: var(--dim); line-height: 1.55; margin: 0; }
.si-card-const { font-size: 0.75rem; color: var(--warm); font-family: var(--mono); margin-top: 0.2rem; }

/* ── Shared controls ── */
.control-group { display: flex; flex-direction: column; gap: 0.25rem; min-width: 120px; flex: 1; }
.control-group label { font-size: 0.78rem; font-weight: 600; color: var(--dim); margin: 0; padding: 0; }
.control-value { font-size: 0.78rem; color: var(--accent); font-family: var(--mono); }

input[type="range"] {
  -webkit-appearance: none; appearance: none;
  width: 100%; height: 6px; border-radius: 3px;
  background: var(--border); outline: none; cursor: pointer;
}
input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none; appearance: none;
  width: 16px; height: 16px; border-radius: 50%;
  background: var(--accent); border: 2px solid var(--panel); cursor: pointer;
}
input[type="range"]::-moz-range-thumb {
  width: 16px; height: 16px; border-radius: 50%;
  background: var(--accent); border: 2px solid var(--panel); cursor: pointer;
}

.btn {
  background: var(--panel2); border: 2px solid var(--border);
  color: var(--dim); border-radius: 0.3rem;
  padding: 0.45rem 1rem; font-size: 0.82rem; cursor: pointer;
  font-family: var(--sans); transition: color 0.15s, border-color 0.15s;
}
.btn:hover { color: var(--text); border-color: var(--accent); }

.dim { color: var(--dim); }

/* ── Toast ── */
.toast {
  position: fixed; bottom: 1.5rem; left: 50%;
  transform: translateX(-50%) translateY(1rem);
  padding: 0.5rem 1.2rem; border-radius: 0.3rem;
  background: var(--accent); color: #0c0d0f;
  font-size: 0.82rem; font-weight: 600;
  opacity: 0; pointer-events: none;
  transition: opacity 0.2s, transform 0.2s; z-index: 10000;
}
.toast.visible { opacity: 1; transform: translateX(-50%) translateY(0); }

.fineprint {
  margin-top: 2rem; padding-top: 1rem;
  border-top: 2px solid var(--line);
  font-size: 0.78rem; color: var(--muted); text-align: center;
}

/* ── Responsive ── */
@media (max-width: 720px) {
  .wrap { padding: 14px 14px 40px; }
  .topbar-content { padding: 0.55rem 14px; }
  .intro-title { font-size: 1.3rem; }
  .section-card { padding: 1rem 1.1rem; }
  .gallery-grid { grid-template-columns: repeat(2, 1fr); }
  .timeline-card { flex: 0 0 220px; }
  .hero-canvas { height: 360px; }
  .converter-input-row, .converter-dimension-row { flex-direction: column; }
  .converter-row { grid-template-columns: 140px 1fr; }
}

@media (max-width: 480px) {
  .gallery-grid { grid-template-columns: 1fr; }
  .hero-canvas { height: 320px; }
  .hero-readouts { grid-template-columns: repeat(2, 1fr); }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}