/* ==========================================================================
   DOUĂ GRADE SUB UNGHIE - STYLESHEET
   Optics / Retinal Biophysics Aesthetic
   ========================================================================== */

:root {
  --bg-main: #070a12;
  --bg-card: #0e1526;
  --bg-card-hover: #141d34;
  --bg-card-subtle: #0b1120;
  --border-card: rgba(56, 189, 248, 0.15);
  --border-focus: #38bdf8;
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --accent-cyan: #38bdf8;
  --accent-blue: #60a5fa;
  --accent-indigo: #818cf8;
  --accent-amber: #f59e0b;
  --accent-emerald: #10b981;
  --accent-rose: #f43f5e;
  
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  --font-serif: "Newsreader", Georgia, Cambria, "Times New Roman", Times, serif;

  --max-w-prose: 760px;
  --max-w-wide: 1080px;
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 18px;
  --radius-full: 9999px;
}

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

html {
  font-size: 16px;
  line-height: 1.6;
  background-color: var(--bg-main);
  color: var(--text-primary);
  font-family: var(--font-sans);
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow-x: hidden;
  position: relative;
}

/* Accessibility: FM-001 strictly defined */
.sr-only {
  position: absolute !important;
  width: 1px !important;
  height: 1px !important;
  padding: 0 !important;
  margin: -1px !important;
  overflow: hidden !important;
  clip: rect(0, 0, 0, 0) !important;
  white-space: nowrap !important;
  border: 0 !important;
}

/* Background Optical Grids */
.bg-optic-mesh {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 800px;
  background: 
    radial-gradient(circle at 50% 120px, rgba(56, 189, 248, 0.12) 0%, rgba(99, 102, 241, 0.04) 45%, transparent 75%),
    linear-gradient(180deg, rgba(7, 10, 18, 0) 0%, var(--bg-main) 100%);
  pointer-events: none;
  z-index: 0;
}

/* Header & Nav */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(7, 10, 18, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}

.nav-container {
  max-width: var(--max-w-wide);
  margin: 0 auto;
  padding: 12px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.brand-link {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: var(--text-primary);
  font-weight: 700;
  font-size: 0.95rem;
  letter-spacing: -0.01em;
}

.brand-badge {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--accent-cyan);
  box-shadow: 0 0 10px var(--accent-cyan);
}

.lang-nav {
  display: flex;
  align-items: center;
  gap: 6px;
  background: rgba(255, 255, 255, 0.05);
  padding: 4px;
  border-radius: var(--radius-full);
  border: 1px solid rgba(255, 255, 255, 0.1);
}

.lang-btn {
  padding: 4px 12px;
  border-radius: var(--radius-full);
  font-size: 0.8rem;
  font-weight: 600;
  text-decoration: none;
  color: var(--text-secondary);
  transition: all 0.15s ease;
}

.lang-btn:hover {
  color: var(--text-primary);
}

.lang-btn.active {
  background: var(--accent-cyan);
  color: #070a12;
}

/* Layout Containers */
.container-prose {
  max-width: var(--max-w-prose);
  margin: 0 auto;
  padding: 0 20px;
  width: 100%;
  position: relative;
  z-index: 1;
}

.container-wide {
  max-width: var(--max-w-wide);
  margin: 0 auto;
  padding: 0 20px;
  width: 100%;
  position: relative;
  z-index: 1;
}

/* Hero Section (Answer-First Minto) */
.hero {
  padding: 60px 0 40px;
  text-align: left;
}

.topic-kicker {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--accent-cyan);
  background: rgba(56, 189, 248, 0.1);
  border: 1px solid rgba(56, 189, 248, 0.25);
  padding: 4px 12px;
  border-radius: var(--radius-full);
  margin-bottom: 20px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.hero-title {
  font-size: clamp(2rem, 5vw, 3.1rem);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.03em;
  color: #ffffff;
  margin-bottom: 20px;
}

.hero-title .highlight {
  background: linear-gradient(135deg, var(--accent-cyan) 0%, var(--accent-indigo) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-conclusion {
  font-size: clamp(1.15rem, 2.2vw, 1.35rem);
  line-height: 1.5;
  color: #cbd5e1;
  margin-bottom: 32px;
  font-weight: 400;
}

.hero-metrics-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 16px;
  margin-top: 32px;
  margin-bottom: 48px;
}

.metric-card {
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-md);
  padding: 20px 18px;
  display: flex;
  flex-direction: column;
  gap: 6px;
  transition: transform 0.2s ease, border-color 0.2s ease;
}

.metric-card:hover {
  transform: translateY(-2px);
  border-color: rgba(56, 189, 248, 0.4);
}

.metric-val {
  font-family: var(--font-mono);
  font-size: 1.75rem;
  font-weight: 800;
  color: var(--accent-cyan);
  line-height: 1.1;
}

.metric-lbl {
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.3;
}

/* Article Body Prose */
.editorial-prose {
  font-size: 1.125rem;
  line-height: 1.75;
  color: #e2e8f0;
}

.editorial-prose p {
  margin-bottom: 24px;
}

.editorial-prose h2 {
  font-size: 1.65rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: #ffffff;
  margin: 48px 0 20px;
  display: flex;
  align-items: center;
  gap: 12px;
}

.editorial-prose h2::before {
  content: "";
  display: inline-block;
  width: 4px;
  height: 1.2em;
  background: var(--accent-cyan);
  border-radius: 2px;
}

.editorial-prose h3 {
  font-size: 1.3rem;
  font-weight: 600;
  color: #f1f5f9;
  margin: 32px 0 16px;
}

.editorial-prose strong {
  color: #ffffff;
  font-weight: 600;
}

.editorial-prose em {
  font-style: italic;
  color: #93c5fd;
}

.editorial-prose blockquote {
  border-left: 3px solid var(--accent-cyan);
  padding: 12px 20px;
  margin: 28px 0;
  background: rgba(56, 189, 248, 0.05);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  color: #cbd5e1;
  font-size: 1.05rem;
}

/* Interactive Component Containers */
.interactive-module {
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-lg);
  padding: 32px 28px;
  margin: 40px 0;
  position: relative;
  overflow: hidden;
}

.module-header {
  margin-bottom: 24px;
}

.module-title {
  font-size: 1.35rem;
  font-weight: 700;
  color: #ffffff;
  display: flex;
  align-items: center;
  gap: 10px;
}

.module-icon {
  color: var(--accent-cyan);
}

.module-desc {
  font-size: 0.95rem;
  color: var(--text-secondary);
  margin-top: 6px;
  line-height: 1.5;
}

/* 1. On-Body Thumb Test Card */
.body-test-box {
  background: linear-gradient(135deg, rgba(56, 189, 248, 0.08) 0%, rgba(99, 102, 241, 0.05) 100%);
  border: 1px solid rgba(56, 189, 248, 0.3);
  border-radius: var(--radius-md);
  padding: 24px;
  margin: 32px 0;
}

.body-test-steps {
  display: flex;
  flex-direction: column;
  gap: 14px;
  margin-top: 16px;
}

.step-item {
  display: flex;
  gap: 14px;
  align-items: flex-start;
}

.step-num {
  background: var(--accent-cyan);
  color: #070a12;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  font-weight: 800;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  margin-top: 2px;
}

.step-content {
  font-size: 1rem;
  color: #e2e8f0;
  line-height: 1.5;
}

/* 2. Stuart Anstis Acuity Wheel Canvas */
.anstis-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 20px;
}

.canvas-wrapper {
  position: relative;
  width: 100%;
  max-width: 600px;
  aspect-ratio: 1 / 1;
  background: #060911;
  border-radius: var(--radius-md);
  border: 1px solid rgba(255, 255, 255, 0.1);
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
}

#anstisCanvas {
  width: 100%;
  height: 100%;
  display: block;
}

.controls-row {
  width: 100%;
  max-width: 600px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  background: rgba(255, 255, 255, 0.03);
  padding: 16px 20px;
  border-radius: var(--radius-md);
  border: 1px solid rgba(255, 255, 255, 0.06);
}

.control-item {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

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

.control-val {
  font-family: var(--font-mono);
  color: var(--accent-cyan);
  font-weight: 700;
}

input[type="range"] {
  -webkit-appearance: none;
  width: 100%;
  height: 6px;
  border-radius: 3px;
  background: rgba(255, 255, 255, 0.15);
  outline: none;
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--accent-cyan);
  cursor: pointer;
  box-shadow: 0 0 10px rgba(56, 189, 248, 0.6);
}

/* 3. Gaze-Contingent Foveal Reader */
.reader-box {
  position: relative;
  width: 100%;
  min-height: 380px;
  background: #090e1c;
  border-radius: var(--radius-md);
  border: 1px solid rgba(56, 189, 248, 0.25);
  padding: 30px;
  user-select: none;
  touch-action: none;
  cursor: crosshair;
  overflow: hidden;
}

.reader-text-layer {
  font-family: var(--font-serif);
  font-size: 1.25rem;
  line-height: 1.8;
  color: #e2e8f0;
  position: relative;
  z-index: 1;
}

.foveal-lens-overlay {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: 2;
}

.reader-toggle-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 16px;
}

.toggle-group {
  display: flex;
  align-items: center;
  gap: 8px;
  background: rgba(255, 255, 255, 0.05);
  padding: 4px;
  border-radius: var(--radius-full);
  border: 1px solid rgba(255, 255, 255, 0.1);
}

.toggle-btn {
  padding: 6px 14px;
  border-radius: var(--radius-full);
  border: none;
  background: transparent;
  color: var(--text-secondary);
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.15s ease;
}

.toggle-btn.active {
  background: var(--accent-cyan);
  color: #070a12;
}

.lens-hint {
  font-size: 0.85rem;
  color: var(--text-muted);
  font-style: italic;
}

/* 4. Foveal Footprint Calculator */
.calc-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

@media (max-width: 768px) {
  .calc-grid {
    grid-template-columns: 1fr;
  }
}

.calc-inputs {
  display: flex;
  flex-direction: column;
  gap: 18px;
}

.preset-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.preset-btn {
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid rgba(255, 255, 255, 0.12);
  color: var(--text-secondary);
  padding: 6px 12px;
  border-radius: var(--radius-sm);
  font-size: 0.8rem;
  cursor: pointer;
  transition: all 0.15s ease;
}

.preset-btn:hover, .preset-btn.active {
  background: rgba(56, 189, 248, 0.15);
  border-color: var(--accent-cyan);
  color: #ffffff;
}

.calc-outputs {
  background: #060911;
  border-radius: var(--radius-md);
  border: 1px solid rgba(56, 189, 248, 0.2);
  padding: 24px;
  display: flex;
  flex-direction: column;
  justify-content: space-around;
  gap: 16px;
}

.output-row {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.out-val-large {
  font-family: var(--font-mono);
  font-size: 2rem;
  font-weight: 800;
  color: var(--accent-cyan);
  line-height: 1.1;
}

.out-val-sub {
  font-size: 0.9rem;
  color: #94a3b8;
}

.out-lbl {
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
}

/* 5. Comparative Anatomy Table */
.table-wrapper {
  width: 100%;
  overflow-x: auto;
  margin: 32px 0;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-card);
}

.data-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.95rem;
}

.data-table th, .data-table td {
  padding: 14px 18px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
}

.data-table th {
  background: rgba(255, 255, 255, 0.04);
  color: #f1f5f9;
  font-weight: 600;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

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

.data-table tr:hover td {
  background: rgba(56, 189, 248, 0.03);
}

.species-name {
  font-weight: 600;
  color: #ffffff;
}

/* Scientific Boundary & Method Notes */
.boundary-box {
  background: rgba(15, 23, 42, 0.6);
  border-left: 3px solid var(--accent-amber);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  padding: 24px 28px;
  margin: 48px 0;
}

.boundary-title {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--accent-amber);
  margin-bottom: 8px;
}

.boundary-text {
  font-size: 0.95rem;
  color: #cbd5e1;
  line-height: 1.6;
}

/* References Section */
.references-section {
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  padding: 48px 0 24px;
  margin-top: 60px;
}

.references-title {
  font-size: 1.2rem;
  font-weight: 700;
  color: #ffffff;
  margin-bottom: 20px;
}

.ref-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.ref-item {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.5;
  padding-left: 24px;
  position: relative;
}

.ref-item::before {
  content: "•";
  position: absolute;
  left: 8px;
  color: var(--accent-cyan);
}

.ref-item a {
  color: var(--accent-cyan);
  text-decoration: none;
}

.ref-item a:hover {
  text-decoration: underline;
}

/* Site Footer */
.site-footer {
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  background: #05070d;
  padding: 40px 0;
  margin-top: auto;
}

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

.footer-meta {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.footer-meta a {
  color: var(--text-secondary);
  text-decoration: none;
}

.footer-meta a:hover {
  color: var(--accent-cyan);
}

.footer-badges {
  display: flex;
  gap: 12px;
  align-items: center;
}

.catalog-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 14px;
  border-radius: var(--radius-full);
  background: rgba(255, 255, 255, 0.06);
  color: #f1f5f9;
  font-size: 0.85rem;
  font-weight: 600;
  text-decoration: none;
  border: 1px solid rgba(255, 255, 255, 0.12);
  transition: all 0.15s ease;
}

.catalog-link:hover {
  background: var(--accent-cyan);
  color: #070a12;
  border-color: var(--accent-cyan);
}

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