:root {
  --bg: #090c10;
  --bg-card: rgba(255, 255, 255, 0.04);
  --bg-card-hover: rgba(255, 255, 255, 0.07);
  --bg-card-active: rgba(245, 158, 11, 0.08);
  --border: rgba(255, 255, 255, 0.1);
  --border-glow: rgba(245, 158, 11, 0.35);
  --text-main: #f8fafc;
  --text-muted: #94a3b8;
  --text-dim: #64748b;
  --accent-amber: #f59e0b;
  --accent-amber-light: #fbbf24;
  --accent-amber-glow: rgba(245, 158, 11, 0.2);
  --accent-cyan: #38bdf8;
  --accent-cyan-glow: rgba(56, 189, 248, 0.2);
  --accent-rose: #f43f5e;
  --accent-emerald: #10b981;
  --card-radius: 14px;
  --transition: all 0.2s cubic-bezier(0.16, 1, 0.3, 1);
  --font-serif: "Charter", "Bitstream Charter", "Sitka Text", "Cambria", Georgia, serif;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, "SF Mono", "Menlo", "Consolas", monospace;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #f8fafc;
    --bg-card: #ffffff;
    --bg-card-hover: #f1f5f9;
    --bg-card-active: #fffbeb;
    --border: #e2e8f0;
    --border-glow: rgba(217, 119, 6, 0.4);
    --text-main: #0f172a;
    --text-muted: #475569;
    --text-dim: #94a3b8;
    --accent-amber: #d97706;
    --accent-amber-light: #b45309;
    --accent-amber-glow: rgba(217, 119, 6, 0.15);
    --accent-cyan: #0284c7;
    --accent-cyan-glow: rgba(2, 132, 199, 0.15);
    --accent-rose: #e11d48;
    --accent-emerald: #059669;
  }
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  background-color: var(--bg);
  color: var(--text-main);
  -webkit-font-smoothing: antialiased;
}

body {
  font-family: var(--font-sans);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.site-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.25rem 2rem;
  max-width: 1000px;
  margin: 0 auto;
  width: 100%;
}

.brand {
  font-family: var(--font-mono);
  font-size: 0.9rem;
  font-weight: 600;
  text-decoration: none;
  color: var(--text-muted);
  letter-spacing: 0.05em;
  transition: var(--transition);
}

.brand:hover {
  color: var(--accent-amber);
}

.lang-switch {
  display: flex;
  gap: 0.5rem;
}

.lang-btn {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  padding: 0.35rem 0.75rem;
  border-radius: 6px;
  text-decoration: none;
  color: var(--text-dim);
  border: 1px solid var(--border);
  transition: var(--transition);
}

.lang-btn.active {
  color: var(--accent-amber);
  border-color: var(--accent-amber);
  background: var(--accent-amber-glow);
  font-weight: 600;
}

.lang-btn:hover:not(.active) {
  color: var(--text-main);
  border-color: var(--text-muted);
}

.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 1.5rem 1.5rem 4rem;
  width: 100%;
}

.hero {
  margin-bottom: 3.5rem;
}

.kicker {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--accent-amber);
  background: var(--accent-amber-glow);
  padding: 0.35rem 0.85rem;
  border-radius: 999px;
  border: 1px solid var(--border-glow);
  margin-bottom: 1.25rem;
}

.hero-title {
  font-family: var(--font-serif);
  font-size: clamp(2.2rem, 5vw, 3.4rem);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.02em;
  margin-bottom: 1.25rem;
  color: var(--text-main);
}

.hero-deck {
  font-size: clamp(1.1rem, 2.5vw, 1.35rem);
  line-height: 1.55;
  color: var(--text-muted);
  font-weight: 400;
  margin-bottom: 2rem;
}

.stat-strip {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1rem;
  margin-bottom: 3rem;
}

.stat-box {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--card-radius);
  padding: 1.25rem;
  transition: var(--transition);
}

.stat-box:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-glow);
}

.stat-value {
  font-family: var(--font-mono);
  font-size: 1.85rem;
  font-weight: 700;
  color: var(--accent-amber);
  margin-bottom: 0.35rem;
}

.stat-value.cyan {
  color: var(--accent-cyan);
}

.stat-value.rose {
  color: var(--accent-rose);
}

.stat-label {
  font-size: 0.85rem;
  color: var(--text-muted);
  line-height: 1.4;
}

/* Tool Sections */
.tool-section {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--card-radius);
  padding: 2rem;
  margin-bottom: 3.5rem;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.15);
}

.tool-header {
  margin-bottom: 1.75rem;
}

.tool-title {
  font-family: var(--font-serif);
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 0.5rem;
}

.tool-desc {
  font-size: 0.95rem;
  color: var(--text-muted);
}

/* Presets */
.preset-group {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
}

.preset-btn {
  font-family: var(--font-sans);
  font-size: 0.85rem;
  padding: 0.45rem 0.9rem;
  border-radius: 8px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-muted);
  cursor: pointer;
  transition: var(--transition);
}

.preset-btn:hover {
  color: var(--text-main);
  border-color: var(--accent-amber);
}

.preset-btn.active {
  background: var(--accent-amber-glow);
  border-color: var(--accent-amber);
  color: var(--accent-amber);
  font-weight: 600;
}

/* Controls */
.control-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1.25rem;
  margin-bottom: 2rem;
}

.control-item {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.control-label {
  display: flex;
  justify-content: space-between;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-main);
}

.control-val {
  font-family: var(--font-mono);
  color: var(--accent-amber);
  font-weight: 600;
}

input[type="range"] {
  -webkit-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;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--accent-amber);
  cursor: pointer;
  box-shadow: 0 0 10px var(--accent-amber-glow);
  transition: transform 0.1s ease;
}

input[type="range"]::-webkit-slider-thumb:hover {
  transform: scale(1.2);
}

/* Result readout */
.calc-results {
  background: rgba(0, 0, 0, 0.25);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1.25rem;
  margin-bottom: 1.5rem;
}

.result-card {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.result-kicker {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  text-transform: uppercase;
  color: var(--text-dim);
  letter-spacing: 0.05em;
}

.result-val {
  font-family: var(--font-mono);
  font-size: 1.7rem;
  font-weight: 700;
  color: var(--accent-amber);
}

.result-val.cyan {
  color: var(--accent-cyan);
}

.result-val.rose {
  color: var(--accent-rose);
}

.result-sub {
  font-size: 0.8rem;
  color: var(--text-muted);
}

.calc-summary-text {
  font-size: 1rem;
  line-height: 1.6;
  color: var(--text-main);
  padding: 1rem 1.25rem;
  background: var(--bg-card);
  border-left: 3px solid var(--accent-amber);
  border-radius: 0 8px 8px 0;
}

/* Universal Scale Spectrum */
.scale-spectrum {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
  margin-bottom: 2rem;
}

.scale-row {
  display: grid;
  grid-template-columns: 180px 1fr 140px;
  align-items: center;
  gap: 1rem;
  padding: 0.75rem 1rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  transition: var(--transition);
}

.scale-row:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-glow);
}

.scale-row.active {
  background: var(--bg-card-active);
  border-color: var(--accent-amber);
}

.scale-name {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-main);
}

.scale-bar-track {
  width: 100%;
  height: 8px;
  background: rgba(255, 255, 255, 0.05);
  border-radius: 4px;
  overflow: hidden;
  position: relative;
}

.scale-bar-fill {
  height: 100%;
  border-radius: 4px;
  background: linear-gradient(90deg, var(--accent-cyan), var(--accent-amber));
  transition: width 0.4s ease;
}

.scale-value {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  font-weight: 600;
  text-align: right;
  color: var(--accent-amber);
}

.scale-detail-card {
  background: rgba(0, 0, 0, 0.25);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
}

.detail-header {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  margin-bottom: 0.75rem;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.detail-title {
  font-family: var(--font-serif);
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--text-main);
}

.detail-rate {
  font-family: var(--font-mono);
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--accent-amber);
}

.detail-body {
  font-size: 0.95rem;
  color: var(--text-muted);
  line-height: 1.55;
  margin-bottom: 1rem;
}

.detail-metrics {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 0.75rem;
  padding-top: 0.75rem;
  border-top: 1px solid var(--border);
}

.metric-item {
  font-size: 0.8rem;
  color: var(--text-dim);
}

.metric-item strong {
  color: var(--text-main);
  font-family: var(--font-mono);
}

/* Volumetric Comparison */
.vol-comparison {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  margin-bottom: 1.5rem;
}

.vol-card {
  background: rgba(0, 0, 0, 0.25);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
  text-align: center;
}

.vol-card.highlight {
  border-color: var(--accent-amber);
  background: var(--bg-card-active);
}

.vol-icon {
  font-size: 2rem;
  margin-bottom: 0.5rem;
}

.vol-title {
  font-family: var(--font-serif);
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  color: var(--text-main);
}

.vol-number {
  font-family: var(--font-mono);
  font-size: 2rem;
  font-weight: 700;
  color: var(--accent-amber);
  margin-bottom: 0.25rem;
}

.vol-unit {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-bottom: 0.75rem;
}

.vol-desc {
  font-size: 0.85rem;
  color: var(--text-muted);
  line-height: 1.45;
}

/* Editorial Prose */
.prose {
  margin-bottom: 3.5rem;
}

.prose h2 {
  font-family: var(--font-serif);
  font-size: 1.8rem;
  font-weight: 700;
  margin: 2.5rem 0 1rem;
  color: var(--text-main);
}

.prose p {
  font-size: 1.05rem;
  line-height: 1.7;
  color: var(--text-muted);
  margin-bottom: 1.35rem;
}

.prose strong {
  color: var(--text-main);
}

.prose-callout {
  background: var(--bg-card);
  border-left: 4px solid var(--accent-cyan);
  border-radius: 0 10px 10px 0;
  padding: 1.25rem 1.5rem;
  margin: 2rem 0;
}

.prose-callout p {
  margin: 0;
  font-size: 0.95rem;
  color: var(--text-main);
}

/* Method Note */
.method-note {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--card-radius);
  padding: 1.75rem;
  margin-bottom: 3.5rem;
}

.method-note h3 {
  font-family: var(--font-mono);
  font-size: 0.95rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-main);
  margin-bottom: 1rem;
}

.method-note p {
  font-size: 0.9rem;
  color: var(--text-dim);
  line-height: 1.6;
  margin-bottom: 0.75rem;
}

.method-note a {
  color: var(--accent-amber);
  text-decoration: none;
}

.method-note a:hover {
  text-decoration: underline;
}

/* Footer & Back to top */
.site-footer {
  border-top: 1px solid var(--border);
  padding: 2.5rem 1.5rem;
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-dim);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.25rem;
}

.footer-links {
  display: flex;
  gap: 1.5rem;
  flex-wrap: wrap;
  justify-content: center;
}

.footer-links a {
  color: var(--text-muted);
  text-decoration: none;
  transition: var(--transition);
}

.footer-links a:hover {
  color: var(--accent-amber);
}

.btt-button {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  padding: 0.5rem 1.25rem;
  border-radius: 999px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-muted);
  cursor: pointer;
  text-decoration: none;
  transition: var(--transition);
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
}

.btt-button:hover {
  color: var(--text-main);
  border-color: var(--accent-amber);
  background: var(--accent-amber-glow);
}

.action-btn {
  display: inline-block;
  font-family: var(--font-sans);
  font-size: 0.9rem;
  font-weight: 600;
  padding: 0.65rem 1.5rem;
  border-radius: 8px;
  background: var(--accent-amber);
  color: #000;
  text-decoration: none;
  transition: var(--transition);
}

.action-btn:hover {
  background: var(--accent-amber-light);
  transform: translateY(-1px);
}

/* Fallback for no-js */
.no-js .interactive-only {
  display: none !important;
}

.no-js .static-fallback {
  display: block !important;
}

.static-fallback {
  display: none;
}

/* Responsive adjustments */
@media (max-width: 640px) {
  .site-header {
    padding: 1rem;
  }

  .container {
    padding: 1rem 1rem 3rem;
  }

  .tool-section {
    padding: 1.25rem;
  }

  .scale-row {
    grid-template-columns: 130px 1fr 100px;
    gap: 0.5rem;
    padding: 0.6rem 0.75rem;
  }

  .scale-name {
    font-size: 0.8rem;
  }

  .scale-value {
    font-size: 0.75rem;
  }

  .vol-comparison {
    grid-template-columns: 1fr;
    gap: 1rem;
  }
}

/* Accessibility / Reduced Motion */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}