/* ==========================================================================
   CYBOU.FR — Sovereign European P2P Architecture (Light Technical Design)
   Engineered for clarity, AI/search engine indexing & transparent systems status
   ========================================================================== */

:root {
  --font-sans: -apple-system, BlinkMacSystemFont, "SF Pro Display", "SF Pro Text", "Segoe UI", Roboto, "Helvetica Neue", sans-serif;
  --font-mono: "SF Mono", Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;

  /* Surfaces & Backgrounds */
  --bg-canvas: #ffffff;
  --bg-subtle: #f8f9fb;
  --bg-surface: #f1f3f6;
  --bg-card: #ffffff;
  --bg-glass: rgba(255, 255, 255, 0.88);

  /* Contrast Container for Logo */
  --bg-logo-tile: #0a0b0e;
  --border-logo-tile: rgba(255, 255, 255, 0.12);

  /* Borders & Dividers */
  --border-subtle: #e5e7eb;
  --border-medium: #d1d5db;
  --border-mint: rgba(16, 185, 129, 0.35);

  /* Typography */
  --text-primary: #111827;
  --text-secondary: #4b5563;
  --text-muted: #6b7280;
  --text-dim: #9ca3af;

  /* Brand Palette (Complementary to cybou.png) */
  --logo-mint: #34d399;
  --logo-mint-glow: #10b981;
  --brand-teal: #059669;
  --brand-teal-dark: #047857;
  --brand-blue: #0284c7;
  --brand-indigo: #4f46e5;
  --status-amber: #d97706;
  --status-red: #dc2626;

  /* Radii */
  --radius-xs: 6px;
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 20px;
  --radius-xl: 28px;
  --radius-pill: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.05);
  --shadow-card: 0 4px 20px rgba(0, 0, 0, 0.05);
  --shadow-card-hover: 0 12px 36px rgba(0, 0, 0, 0.09), 0 0 24px rgba(16, 185, 129, 0.12);
  --shadow-logo: 0 6px 20px rgba(0, 0, 0, 0.15), 0 0 20px rgba(52, 211, 153, 0.25);

  /* Transitions */
  --transition-fast: 0.18s cubic-bezier(0.16, 1, 0.3, 1);
  --transition-smooth: 0.3s cubic-bezier(0.16, 1, 0.3, 1);
}

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

html {
  font-family: var(--font-sans);
  background-color: var(--bg-canvas);
  color: var(--text-primary);
  scroll-behavior: smooth;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  overflow-x: hidden;
  background: var(--bg-canvas);
  line-height: 1.6;
}

::selection {
  background: rgba(16, 185, 129, 0.2);
  color: var(--brand-teal-dark);
}

a {
  color: inherit;
  text-decoration: none;
}

/* ==========================================================================
   Header & Navigation (Apple Style Frosted Glass)
   ========================================================================== */

.nav-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  height: 64px;
  background: var(--bg-glass);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid var(--border-subtle);
}

.nav-container {
  max-width: 1140px;
  margin: 0 auto;
  padding: 0 24px;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 1.15rem;
  font-weight: 600;
  letter-spacing: -0.015em;
  color: var(--text-primary);
}

.nav-brand-group {
  display: flex;
  align-items: center;
  gap: 10px;
}

/* Logo Contrast Squircle Tile */
.logo-tile {
  width: 36px;
  height: 36px;
  background: var(--bg-logo-tile);
  border: 1px solid var(--border-logo-tile);
  border-radius: 9px;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.12);
  flex-shrink: 0;
}

.logo-tile img {
  width: 26px;
  height: 26px;
  object-fit: contain;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 26px;
  list-style: none;
}

.nav-links a {
  font-size: 0.88rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition: color var(--transition-fast);
}

.nav-links a:hover {
  color: var(--text-primary);
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: 14px;
}

.lang-switch {
  display: flex;
  align-items: center;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-pill);
  padding: 2px;
  font-size: 0.75rem;
  font-weight: 600;
}

.lang-btn {
  background: transparent;
  border: none;
  color: var(--text-muted);
  padding: 4px 10px;
  border-radius: var(--radius-pill);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.lang-btn.active {
  color: var(--text-primary);
  background: #ffffff;
  box-shadow: var(--shadow-sm);
}

.github-link {
  width: 38px;
  height: 38px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--border-subtle);
  border-radius: 50%;
  background: #ffffff;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.github-link:hover {
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.github-link img {
  width: 22px;
  height: 22px;
}

.menu-toggle {
  display: none;
  width: 38px;
  height: 38px;
  align-items: center;
  justify-content: center;
  padding: 0;
  border: 1px solid var(--border-subtle);
  border-radius: 50%;
  background: #ffffff;
  color: var(--text-primary);
  font: inherit;
  font-size: 0.84rem;
  font-weight: 600;
  cursor: pointer;
  box-shadow: var(--shadow-sm);
  transition: background var(--transition-fast), transform var(--transition-fast);
}

.menu-toggle:hover,
.menu-toggle[aria-expanded="true"] {
  background: var(--bg-subtle);
}

.menu-toggle:active {
  transform: scale(0.96);
}

.mobile-menu {
  position: absolute;
  top: 64px;
  left: 0;
  right: 0;
  padding: 12px 24px 20px;
  display: grid;
  gap: 4px;
  background: rgba(255, 255, 255, 0.98);
  border-bottom: 1px solid var(--border-subtle);
  box-shadow: var(--shadow-card);
}

.mobile-menu[hidden] {
  display: none;
}

.mobile-menu a {
  padding: 12px 10px;
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  font-weight: 500;
}

.mobile-menu a:hover,
.mobile-menu a:focus-visible {
  color: var(--text-primary);
  background: var(--bg-subtle);
}

/* ==========================================================================
   Hero Section
   ========================================================================== */

.hero-section {
  position: relative;
  padding: 140px 24px 70px;
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  background: radial-gradient(ellipse 90% 55% at 50% -5%, rgba(52, 211, 153, 0.15), rgba(243, 244, 246, 0.6) 45%, transparent 80%);
}

/* Hero Big Logo Presentation Tile */
.hero-logo-box {
  width: 90px;
  height: 90px;
  background: var(--bg-logo-tile);
  border: 1px solid rgba(255, 255, 255, 0.15);
  border-radius: 22px;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-logo);
  margin-bottom: 24px;
  padding: 12px;
  transition: transform var(--transition-smooth);
}

.hero-logo-box:hover {
  transform: translateY(-2px) scale(1.02);
}

.hero-logo-box img {
  width: 100%;
  height: 100%;
  object-fit: contain;
}

.hero-tag {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 16px;
  background: #ffffff;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-pill);
  font-size: 0.84rem;
  font-weight: 500;
  color: var(--text-secondary);
  box-shadow: var(--shadow-sm);
  margin-bottom: 20px;
}

.hero-tag svg {
  color: var(--brand-teal-dark);
  flex-shrink: 0;
}

.hero-title {
  font-size: clamp(2.8rem, 6vw, 4.8rem);
  font-weight: 700;
  letter-spacing: -0.035em;
  line-height: 1.08;
  margin-bottom: 20px;
  max-width: 920px;
  color: var(--text-primary);
}

.hero-title .accent-text {
  background: linear-gradient(135deg, #047857 0%, #059669 40%, #10b981 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-subtitle {
  font-size: clamp(1.15rem, 2.2vw, 1.45rem);
  font-weight: 400;
  color: var(--text-secondary);
  max-width: 760px;
  line-height: 1.5;
  margin-bottom: 32px;
  letter-spacing: -0.015em;
}

/* Honest Status Alert Banner */
.status-callout {
  max-width: 820px;
  width: 100%;
  background: #fffbeb;
  border: 1px solid #fde68a;
  border-radius: var(--radius-md);
  padding: 16px 20px;
  text-align: left;
  display: flex;
  align-items: flex-start;
  gap: 14px;
  margin-bottom: 36px;
  box-shadow: var(--shadow-sm);
}

.status-callout-icon {
  color: #b45309;
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-top: 2px;
}

.status-callout-text h4 {
  font-size: 0.95rem;
  font-weight: 600;
  color: #92400e;
  margin-bottom: 4px;
}

.status-callout-text p {
  font-size: 0.88rem;
  color: #78350f;
  line-height: 1.45;
}

.hero-buttons {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 14px;
  flex-wrap: wrap;
}

.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--text-primary);
  color: #ffffff;
  padding: 12px 26px;
  border-radius: var(--radius-pill);
  font-size: 0.98rem;
  font-weight: 500;
  box-shadow: var(--shadow-sm);
  transition: all var(--transition-fast);
}

.btn-primary:hover {
  background: #000000;
  transform: translateY(-1px);
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.15);
}

.btn-secondary {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: #ffffff;
  color: var(--text-primary);
  border: 1px solid var(--border-medium);
  padding: 12px 24px;
  border-radius: var(--radius-pill);
  font-size: 0.98rem;
  font-weight: 500;
  box-shadow: var(--shadow-sm);
  transition: all var(--transition-fast);
}

.btn-secondary:hover {
  background: var(--bg-subtle);
  border-color: var(--text-muted);
  transform: translateY(-1px);
}

/* ==========================================================================
   General Section Layout
   ========================================================================== */

.section {
  padding: 90px 24px;
  max-width: 1140px;
  margin: 0 auto;
}

.section-header {
  text-align: center;
  max-width: 780px;
  margin: 0 auto 50px;
}

.section-label {
  font-size: 0.82rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--brand-teal-dark);
  margin-bottom: 10px;
}

.section-title {
  font-size: clamp(2.1rem, 4vw, 3.1rem);
  font-weight: 700;
  letter-spacing: -0.025em;
  line-height: 1.15;
  color: var(--text-primary);
  margin-bottom: 16px;
}

.section-description {
  font-size: 1.15rem;
  line-height: 1.5;
  color: var(--text-secondary);
}

/* ==========================================================================
   Implementation Status Matrix (Transparent Technical Ledger)
   ========================================================================== */

.status-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.status-card {
  background: #ffffff;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 28px;
  box-shadow: var(--shadow-card);
  display: flex;
  flex-direction: column;
}

.status-card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 18px;
  padding-bottom: 14px;
  border-bottom: 1px solid var(--border-subtle);
}

.status-card-header h3 {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text-primary);
}

.badge-done {
  font-size: 0.72rem;
  font-weight: 600;
  color: #065f46;
  background: #d1fae5;
  padding: 3px 8px;
  border-radius: var(--radius-pill);
}

.badge-wip {
  font-size: 0.72rem;
  font-weight: 600;
  color: #92400e;
  background: #fef3c7;
  padding: 3px 8px;
  border-radius: var(--radius-pill);
}

.badge-planned {
  font-size: 0.72rem;
  font-weight: 600;
  color: #374151;
  background: #f3f4f6;
  padding: 3px 8px;
  border-radius: var(--radius-pill);
}

.status-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 12px;
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.status-list li {
  position: relative;
  padding-left: 22px;
  line-height: 1.45;
}

.status-list li::before {
  content: "•";
  position: absolute;
  left: 6px;
  color: var(--brand-teal);
  font-size: 1.2rem;
  line-height: 1;
}

.status-card.wip .status-list li::before {
  color: var(--status-amber);
}

.status-card.planned .status-list li::before {
  color: var(--text-muted);
}

/* ==========================================================================
   Architecture Pillars (Bento Grid)
   ========================================================================== */

.bento-grid {
  display: grid;
  grid-template-columns: repeat(12, 1fr);
  gap: 24px;
}

.bento-card {
  background: #ffffff;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: 34px;
  box-shadow: var(--shadow-card);
  transition: transform var(--transition-smooth), border-color var(--transition-smooth), box-shadow var(--transition-smooth);
}

.bento-card:hover {
  transform: translateY(-3px);
  border-color: var(--border-mint);
  box-shadow: var(--shadow-card-hover);
}

.bento-span-8 { grid-column: span 8; }
.bento-span-4 { grid-column: span 4; }
.bento-span-6 { grid-column: span 6; }
.bento-span-12 { grid-column: span 12; }

.card-icon {
  width: 44px;
  height: 44px;
  border-radius: var(--radius-md);
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-primary);
  margin-bottom: 20px;
  transition: all var(--transition-fast);
}

.card-icon svg {
  color: var(--brand-teal-dark);
  transition: transform var(--transition-fast);
}

.bento-card:hover .card-icon {
  background: #ecfdf5;
  border-color: #a7f3d0;
}

.bento-card:hover .card-icon svg {
  transform: scale(1.08);
}

.card-content h3 {
  font-size: 1.35rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 10px;
  letter-spacing: -0.015em;
}

.card-content p {
  font-size: 1rem;
  color: var(--text-secondary);
  line-height: 1.55;
}

.code-snippet {
  margin-top: 20px;
  padding: 14px;
  background: var(--bg-subtle);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: var(--text-secondary);
  line-height: 1.4;
}

/* ==========================================================================
   Protocol Flow (MailTx Technical Pipeline)
   ========================================================================== */

.flow-container {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
}

.flow-step {
  background: #ffffff;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 26px 20px;
  box-shadow: var(--shadow-sm);
  transition: all var(--transition-fast);
}

.flow-step:hover {
  border-color: var(--border-mint);
  box-shadow: var(--shadow-card);
  transform: translateY(-2px);
}

.step-num {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--brand-teal-dark);
  font-weight: 700;
  margin-bottom: 12px;
}

.step-title {
  font-size: 1.08rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 8px;
}

.step-desc {
  font-size: 0.88rem;
  color: var(--text-secondary);
  line-height: 1.45;
}

/* ==========================================================================
   AI & Search Engine Architecture Factsheet (Semantic Technical Grid)
   ========================================================================== */

.factsheet-box {
  background: var(--bg-subtle);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: 36px;
  margin-top: 40px;
}

.factsheet-title {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 20px;
  display: flex;
  align-items: center;
  gap: 10px;
}

.factsheet-title svg {
  color: var(--brand-teal-dark);
  flex-shrink: 0;
}

.tech-spec-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 20px;
}

.spec-item {
  background: #ffffff;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 18px 20px;
}

.spec-item dt {
  font-size: 0.78rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  margin-bottom: 6px;
}

.spec-item dd {
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--text-primary);
  line-height: 1.4;
}

.spec-item code {
  font-family: var(--font-mono);
  background: var(--bg-surface);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.85rem;
}

/* ==========================================================================
   FAQ Section (Apple Style Cards & PQ by Design Callout)
   ========================================================================== */

.faq-grid {
  display: flex;
  flex-direction: column;
  gap: 0;
  max-width: 900px;
  margin: 0 auto;
  background: rgba(255, 255, 255, 0.88);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-card);
  overflow: hidden;
}

.faq-card {
  position: relative;
  background: transparent;
  border-bottom: 1px solid var(--border-subtle);
  transition: background 220ms ease;
}

.faq-card:last-child {
  border-bottom: none;
}

.faq-card.pq-focus {
  background: linear-gradient(90deg, rgba(209, 250, 229, 0.5), rgba(255, 255, 255, 0) 55%);
}

.faq-card:hover,
.faq-card.is-open {
  background-color: rgba(248, 250, 252, 0.9);
}

.faq-trigger {
  width: 100%;
  min-height: 76px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding: 22px 28px;
  border: 0;
  background: transparent;
  color: inherit;
  text-align: left;
  cursor: pointer;
  font: inherit;
}

.faq-trigger:focus-visible {
  outline: 3px solid rgba(5, 150, 105, 0.22);
  outline-offset: -3px;
}

.faq-heading {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 8px;
}

.faq-badge-pq {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--brand-teal-dark);
  background: #d1fae5;
  border: 1px solid #a7f3d0;
  padding: 2px 8px;
  border-radius: var(--radius-pill);
  margin-bottom: 0;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.faq-question {
  display: block;
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--text-primary);
  letter-spacing: -0.01em;
  line-height: 1.35;
}

.faq-chevron {
  flex: 0 0 auto;
  color: var(--text-muted);
  transition: transform 260ms cubic-bezier(0.4, 0, 0.2, 1), color 220ms ease;
}

.faq-card.is-open .faq-chevron {
  color: var(--brand-teal-dark);
  transform: rotate(180deg);
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  opacity: 0;
  padding: 0 72px 0 28px;
  font-size: 0.95rem;
  color: var(--text-secondary);
  line-height: 1.6;
  transition: max-height 360ms cubic-bezier(0.4, 0, 0.2, 1), opacity 220ms ease, padding 300ms ease;
}

.faq-card.is-open .faq-answer {
  max-height: 560px;
  opacity: 1;
  padding-bottom: 26px;
}

.faq-answer p:not(:last-child) {
  margin-bottom: 10px;
}

.faq-answer strong {
  color: var(--text-primary);
}

.faq-answer code {
  font-family: var(--font-mono);
  background: var(--bg-surface);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.85rem;
  color: var(--brand-teal-dark);
}

/* ==========================================================================
   Footer
   ========================================================================== */

.footer {
  border-top: 1px solid var(--border-subtle);
  background: #f8f9fb;
  padding: 60px 24px 40px;
  font-size: 0.84rem;
  color: var(--text-muted);
}

.footer-container {
  max-width: 1140px;
  margin: 0 auto;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 40px;
  margin-bottom: 40px;
}

.footer-brand-title {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 12px;
}

.footer-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.footer-links a {
  color: var(--text-secondary);
  transition: color var(--transition-fast);
}

.footer-links a:hover {
  color: var(--text-primary);
}

.footer-bottom {
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-top: 1px solid var(--border-subtle);
  padding-top: 24px;
  flex-wrap: wrap;
  gap: 16px;
}

.card-metric {
  font-size: 1.8rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text-primary);
  margin-top: 24px;
}

.card-metric-label {
  font-size: 0.82rem;
  color: var(--text-muted);
  font-weight: 500;
  margin-top: 4px;
}

/* Responsive */
@media (max-width: 992px) {
  .status-grid { grid-template-columns: 1fr; }
  .bento-span-8, .bento-span-4, .bento-span-6 { grid-column: span 12; }
  .flow-container { grid-template-columns: 1fr 1fr; }
  .tech-spec-grid { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 1400px) {
  .desktop-nav { display: none; }
  .menu-toggle { display: inline-flex; align-items: center; justify-content: center; }
}

@media (min-width: 1401px) {
  .mobile-menu { display: none !important; }
}

@media (max-width: 640px) {
  .nav-container { padding: 0 16px; }
  .nav-brand { gap: 8px; }
  .nav-actions { gap: 8px; }
  .lang-btn { padding: 4px 8px; }
  .flow-container { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; }
  .faq-trigger { min-height: 68px; padding: 18px 20px; gap: 16px; }
  .faq-question { font-size: 1rem; }
  .faq-answer { padding-left: 20px; padding-right: 48px; }
}