:root {
  --bg: #f6f7fb;
  --bg-soft: #eef2ff;
  --panel: rgba(255,255,255,0.88);
  --panel-strong: rgba(255,255,255,0.96);
  --line: rgba(15,23,42,0.10);
  --line-strong: rgba(15,23,42,0.16);
  --text: #0f172a;
  --soft: #334155;
  --muted: #64748b;
  --button: rgba(255,255,255,0.92);
  --button-line: rgba(15,23,42,0.12);
  --axis: #94a3b8;
  --axis-text: #334155;
  --glow-a: rgba(34, 211, 238, 0.18);
  --glow-b: rgba(168, 85, 247, 0.16);
  --glow-c: rgba(99, 102, 241, 0.10);
  --live: #10b981;
  --attenuated: #f59e0b;
  --extinct: #f43f5e;
  --accent: #8b5cf6;
  --shadow: 0 24px 70px rgba(15, 23, 42, 0.08);
}

html[data-theme="dark"] {
  --bg: #060816;
  --bg-soft: #0b1020;
  --panel: rgba(11, 15, 28, 0.82);
  --panel-strong: rgba(14, 19, 34, 0.94);
  --line: rgba(148,163,184,0.14);
  --line-strong: rgba(148,163,184,0.22);
  --text: #f8fafc;
  --soft: #dbe3f0;
  --muted: #9aa8be;
  --button: rgba(15, 23, 42, 0.72);
  --button-line: rgba(148,163,184,0.18);
  --axis: rgba(148,163,184,0.42);
  --axis-text: rgba(241,245,249,0.88);
  --glow-a: rgba(34, 211, 238, 0.14);
  --glow-b: rgba(168, 85, 247, 0.18);
  --glow-c: rgba(99, 102, 241, 0.11);
  --shadow: 0 30px 80px rgba(0, 0, 0, 0.42);
}

html[data-lang="fr"] .lang-en { display: none !important; }
html[data-lang="en"] .lang-fr { display: none !important; }
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  min-height: 100vh;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background:
    radial-gradient(circle at 10% 0%, var(--glow-a), transparent 26%),
    radial-gradient(circle at 92% 0%, var(--glow-b), transparent 28%),
    radial-gradient(circle at 50% 100%, var(--glow-c), transparent 30%),
    linear-gradient(180deg, var(--bg-soft) 0%, var(--bg) 52%, var(--bg) 100%);
  color: var(--text);
  line-height: 1.65;
}

a { color: inherit; }
img { max-width: 100%; display: block; }
button { font: inherit; }

.aurora {
  position: fixed;
  inset: auto;
  pointer-events: none;
  filter: blur(70px);
  opacity: 0.7;
  z-index: 0;
}
.aurora-a { width: 360px; height: 360px; top: 80px; left: -80px; background: var(--glow-a); }
.aurora-b { width: 320px; height: 320px; top: 120px; right: -80px; background: var(--glow-b); }
.aurora-c { width: 420px; height: 420px; bottom: -160px; left: calc(50% - 210px); background: var(--glow-c); }

.container {
  width: min(1240px, calc(100vw - 32px));
  margin: 0 auto;
  position: relative;
  z-index: 1;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 30;
  backdrop-filter: blur(16px);
  background: color-mix(in srgb, var(--bg) 78%, transparent);
  border-bottom: 1px solid var(--line);
}

.header-row {
  display: grid;
  grid-template-columns: auto 1fr auto;
  align-items: center;
  gap: 20px;
  padding: 16px 0;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
}
.brand-mark {
  width: 46px;
  height: 46px;
  border-radius: 16px;
  display: grid;
  place-items: center;
  border: 1px solid var(--line-strong);
  background: linear-gradient(180deg, color-mix(in srgb, var(--button) 82%, transparent), color-mix(in srgb, var(--button) 62%, transparent));
  box-shadow: inset 0 1px 0 rgba(255,255,255,0.10);
}
.brand strong { display: block; font-size: 1rem; letter-spacing: -0.02em; }
.brand small { display: block; color: var(--muted); font-size: 0.84rem; }

.desktop-nav {
  display: flex;
  justify-content: center;
  gap: 6px;
  flex-wrap: wrap;
}
.desktop-nav a {
  text-decoration: none;
  color: var(--soft);
  padding: 10px 12px;
  border-radius: 14px;
  transition: background-color 0.2s ease, color 0.2s ease;
}
.desktop-nav a:hover {
  background: color-mix(in srgb, var(--button) 82%, transparent);
  color: var(--text);
}

.toolbar {
  display: flex;
  gap: 10px;
}
.toolbar-btn {
  border: 1px solid var(--button-line);
  background: var(--button);
  color: var(--text);
  min-height: 44px;
  padding: 10px 14px;
  border-radius: 16px;
  cursor: pointer;
}
.toolbar-btn:hover { filter: brightness(1.04); }

.layout {
  display: grid;
  gap: 24px;
  padding: 34px 0 48px;
}
.section-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.2fr) minmax(300px, 0.8fr);
  gap: 24px;
}

.panel {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 30px;
  box-shadow: var(--shadow);
  overflow: hidden;
}
.panel-main,
.panel-side {
  padding: 28px;
}
.panel-hero {
  display: grid;
  grid-template-columns: minmax(0, 1.2fr) minmax(320px, 0.8fr);
}
.hero-copy,
.hero-side {
  padding: 34px;
}
.hero-side {
  border-left: 1px solid var(--line);
  background: color-mix(in srgb, var(--panel-strong) 82%, transparent);
}

.eyebrow,
.logic-legend,
.file-grid,
.cta-row,
.result-strip {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}
.tag,
.legend-chip,
.file-chip {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  min-height: 36px;
  padding: 8px 12px;
  border-radius: 999px;
  border: 1px solid var(--button-line);
  background: color-mix(in srgb, var(--button) 84%, transparent);
  color: var(--text);
}
.tag { font-size: 0.9rem; font-weight: 600; }

.hero-copy h1 {
  margin: 18px 0 0;
  font-size: clamp(2.2rem, 4vw, 4.3rem);
  line-height: 1.03;
  letter-spacing: -0.05em;
  max-width: 12ch;
}
.lede {
  margin: 18px 0 0;
  max-width: 62ch;
  color: var(--soft);
  font-size: 1.02rem;
}
.cta-row { margin-top: 22px; }
.cta {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 48px;
  padding: 12px 16px;
  border-radius: 16px;
  border: 1px solid var(--button-line);
  background: var(--button);
  color: var(--text);
  text-decoration: none;
  font-weight: 700;
}
.cta:hover { filter: brightness(1.04); }

.stat-grid,
.bullet-stack,
.insight-grid,
.chart-grid,
.formula-grid {
  display: grid;
  gap: 16px;
}
.stat-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.insight-grid,
.chart-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.formula-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.appendix-formulas { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.formula-card--full { grid-column: 1 / -1; }

.stat-card,
.bullet-card,
.logic-card,
.chart-card,
.formula-card,
.result-box {
  background: color-mix(in srgb, var(--panel-strong) 84%, transparent);
  border: 1px solid var(--line);
  border-radius: 24px;
  padding: 18px;
  min-width: 0;
}
.stat-label,
.section-kicker,
.logic-step,
.mini-label,
.formula-note,
.formula-name {
  display: inline-block;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.11em;
  font-weight: 800;
}
.stat-label,
.section-kicker,
.formula-note { color: var(--accent); }
.stat-card strong,
.bullet-card strong,
.result-box strong,
.logic-card h3,
.chart-card h3,
.formula-name {
  color: var(--text);
}
.stat-card p,
.bullet-card p,
.logic-card p,
.chart-card p,
.formula-copy,
.small-text,
.panel p,
.limit-list {
  color: var(--soft);
}
.section-head h2 {
  margin: 6px 0 0;
  font-size: clamp(1.55rem, 2.3vw, 2.35rem);
  line-height: 1.08;
  letter-spacing: -0.03em;
}
.section-intro,
.section-head + p,
.panel-main > p:first-of-type {
  margin-top: 12px;
}

.parameter-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
  margin-top: 18px;
}

.formula-card--parameter {
  padding: 18px;
}

.formula-stage--parameter {
  margin-top: 14px;
  min-height: 132px;
  padding: 14px 18px;
  justify-content: flex-start;
  overflow-x: auto;
  overflow-y: hidden;
  scrollbar-width: thin;
  scrollbar-color: var(--muted) transparent;
}
.formula-stage--parameter::-webkit-scrollbar { height: 10px; }
.formula-stage--parameter::-webkit-scrollbar-thumb { background: rgba(148,163,184,0.4); border-radius: 999px; }

.formula-image--parameter {
  height: 76px;
  max-width: none;
}

.formula-stage--parameter-text {
  justify-content: center;
  overflow: hidden;
  padding: 14px 18px;
}

.parameter-equation {
  display: inline-flex;
  align-items: baseline;
  justify-content: center;
  gap: 0.08em;
  width: 100%;
  color: var(--text);
  font-family: "STIX Two Text", "Cambria Math", "Times New Roman", serif;
  font-size: clamp(2rem, 3.4vw, 2.9rem);
  font-weight: 500;
  line-height: 1.05;
  letter-spacing: -0.03em;
  white-space: nowrap;
  text-align: center;
}

.parameter-equation sub {
  font-size: 0.52em;
  line-height: 1;
  position: relative;
  bottom: -0.08em;
}

.math-var {
  font-style: italic;
}

.formula-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 14px;
  flex-wrap: wrap;
}
.formula-name {
  font-size: 0.94rem;
  letter-spacing: -0.01em;
  text-transform: none;
}
.formula-copy { margin: 12px 0 0; }
.formula-card--compact { padding: 16px; }
.formula-card--compact .formula-meta { align-items: baseline; }
.formula-stage {
  margin-top: 16px;
  min-width: 0;
  border-radius: 20px;
  border: 1px solid var(--line);
  background: rgba(2, 6, 23, 0.22);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 12px 14px;
  overflow: hidden;
}
html[data-theme="light"] .formula-stage {
  background: rgba(248, 250, 252, 0.88);
}
.formula-stage--scroll {
  overflow-x: auto;
  overflow-y: hidden;
  justify-content: flex-start;
  scrollbar-width: thin;
  scrollbar-color: var(--muted) transparent;
}
.formula-stage--scroll::-webkit-scrollbar { height: 10px; }
.formula-stage--scroll::-webkit-scrollbar-thumb { background: rgba(148,163,184,0.4); border-radius: 999px; }
.formula-stage--sm { min-height: 110px; }
.formula-stage--md { min-height: 118px; }
.formula-stage--lg { min-height: 132px; }
.formula-stage--xl { min-height: 146px; }

.formula-image {
  flex: 0 0 auto;
  width: auto;
  max-width: none;
  height: auto;
  display: block;
  margin-inline: auto;
}
.formula-image--sm { height: 54px; }
.formula-image--md { height: 62px; }
.formula-image--lg { height: 74px; }
.formula-image--xl { height: 84px; }

html[data-theme="dark"] .formula-image {
  filter: invert(1) hue-rotate(180deg) contrast(1.12);
}

.logic-flow {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 16px;
  margin-top: 18px;
}
.logic-card {
  position: relative;
  padding-top: 20px;
}
.logic-card::before {
  content: "";
  position: absolute;
  inset: 0 auto auto 0;
  width: 100%;
  height: 3px;
  border-radius: 999px;
}
.logic-card--live::before { background: var(--live); }
.logic-card--attenuated::before { background: var(--attenuated); }
.logic-card--extinct::before { background: var(--extinct); }
.logic-step {
  color: var(--muted);
  margin-bottom: 8px;
}
.legend-chip i {
  width: 10px;
  height: 10px;
  border-radius: 999px;
  display: inline-block;
}
.legend-chip--live i { background: var(--live); }
.legend-chip--attenuated i { background: var(--attenuated); }
.legend-chip--extinct i { background: var(--extinct); }

.file-grid { margin-top: 18px; }
.file-chip {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  border-radius: 18px;
  padding-inline: 14px;
}

.chart-card svg { margin-top: 10px; }
.chart-svg { width: 100%; height: auto; display: block; }
.result-strip { margin-top: 18px; }
.result-box {
  display: flex;
  flex-direction: column;
  gap: 6px;
  min-height: 96px;
  justify-content: center;
}
.result-box span { color: var(--soft); }

.limit-list {
  margin: 0;
  padding-left: 20px;
}
.signature-panel {
  display: flex;
  flex-direction: column;
  justify-content: center;
}
.accent-card {
  background: linear-gradient(180deg, color-mix(in srgb, var(--panel-strong) 92%, transparent), color-mix(in srgb, var(--panel-strong) 78%, #8b5cf6 6%));
}

.site-footer {
  position: relative;
  z-index: 1;
  border-top: 1px solid var(--line);
  padding: 20px 0 34px;
}
.footer-row {
  color: var(--muted);
  text-align: center;
}

@media (max-width: 1120px) {
  .panel-hero,
  .section-grid,
  .formula-grid,
  .chart-grid,
  .insight-grid,
  .stat-grid,
  .appendix-formulas,
  .logic-flow {
    grid-template-columns: 1fr;
  }
  .hero-side {
    border-left: none;
    border-top: 1px solid var(--line);
  }
}

@media (max-width: 900px) {
  .header-row {
    grid-template-columns: 1fr;
    justify-items: stretch;
  }
  .desktop-nav {
    display: none;
  }
  .toolbar {
    justify-content: flex-end;
    flex-wrap: wrap;
  }
}

@media (max-width: 720px) {
  .container { width: min(100vw - 20px, 100%); }
  .hero-copy,
  .hero-side,
  .panel-main,
  .panel-side { padding: 22px; }
  .hero-copy h1 { max-width: none; font-size: clamp(2rem, 10vw, 2.8rem); }
  .toolbar { width: 100%; }
  .toolbar-btn { flex: 1 1 0; }
  .cta-row { flex-direction: column; }
  .cta { width: 100%; }
  .parameter-grid { grid-template-columns: 1fr; }
  .formula-stage--parameter { min-height: 118px; padding: 12px 14px; }
  .formula-image--parameter { height: 64px; }
  .parameter-equation { font-size: clamp(1.8rem, 7vw, 2.35rem); }
  .formula-image--sm { height: 46px; }
  .formula-image--md { height: 52px; }
  .formula-image--lg { height: 60px; }
  .formula-image--xl { height: 68px; }
  .formula-stage--sm { min-height: 96px; }
  .formula-stage--md { min-height: 104px; }
  .formula-stage--lg { min-height: 116px; }
  .formula-stage--xl { min-height: 126px; }
}