:root {
  --bg: #f4f6fb;
  --bg-card: #ffffff;
  --text: #1b2235;
  --text-muted: #5b6577;
  --primary: #2d5bff;
  --primary-dark: #1e44cc;
  --primary-soft: #e6edff;
  --accent: #0bbf8a;
  --danger: #d93a4c;
  --border: #e2e6f0;
  --shadow: 0 1px 3px rgba(20, 30, 60, 0.04), 0 8px 24px rgba(20, 30, 60, 0.06);
  --radius: 14px;
  --radius-sm: 8px;
  --font: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
}

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.5;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.container {
  max-width: 1120px;
  margin: 0 auto;
  padding: 0 20px;
}

/* ============ HEADER ============ */
.site-header {
  background: linear-gradient(135deg, #2d5bff 0%, #6a8bff 100%);
  color: #fff;
  padding: 48px 0 72px;
  position: relative;
  overflow: hidden;
}

.site-header.compact {
  padding: 20px 0 24px;
}

.site-header::after {
  content: "";
  position: absolute;
  right: -60px;
  top: -60px;
  width: 320px;
  height: 320px;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.08);
}

.site-header::before {
  content: "";
  position: absolute;
  left: -40px;
  bottom: -100px;
  width: 260px;
  height: 260px;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.06);
}

.site-header.compact::before,
.site-header.compact::after {
  display: none;
}

.header-inner {
  position: relative;
  z-index: 1;
}

.logo-link {
  display: inline-flex;
  align-items: center;
  gap: 14px;
  color: #fff;
  text-decoration: none;
  font-weight: 700;
  letter-spacing: -0.01em;
  font-size: clamp(1.25rem, 2vw, 1.55rem);
}

.logo-link:hover {
  opacity: 0.92;
}

.logo {
  margin: 0;
  font-size: clamp(1.6rem, 2.4vw, 2.2rem);
  display: flex;
  align-items: center;
  gap: 14px;
  font-weight: 700;
  letter-spacing: -0.01em;
}

.logo-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  background: #fff;
  color: var(--primary);
  border-radius: 12px;
  font-size: 1.6rem;
  font-weight: 800;
  box-shadow: 0 6px 18px rgba(0, 0, 0, 0.18);
  flex-shrink: 0;
}

.site-header.compact .logo-mark {
  width: 36px;
  height: 36px;
  font-size: 1.2rem;
  border-radius: 9px;
}

.hero-title {
  margin: 20px 0 0;
  font-size: clamp(1.8rem, 3.5vw, 2.6rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.15;
  max-width: 720px;
}

.tagline {
  margin: 12px 0 0;
  opacity: 0.92;
  font-size: 1.05rem;
  max-width: 640px;
}

/* ============ TABS ============ */
.tabs {
  background: #fff;
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 10;
  margin-top: -24px;
  border-top-left-radius: 20px;
  border-top-right-radius: 20px;
  box-shadow: var(--shadow);
}

.tabs-inner {
  display: flex;
  gap: 8px;
  overflow-x: auto;
  padding: 14px 20px;
  scrollbar-width: thin;
}

.tab {
  background: transparent;
  color: var(--text-muted);
  border: 1px solid transparent;
  padding: 10px 18px;
  border-radius: 999px;
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  white-space: nowrap;
  transition: background 0.15s ease, color 0.15s ease, border-color 0.15s ease;
}

.tab:hover {
  background: var(--primary-soft);
  color: var(--primary-dark);
}

.tab.active {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
}

/* ============ MAIN ============ */
.main {
  padding: 32px 20px 24px;
}

.tab-panel {
  display: none;
  grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
  gap: 20px;
}

.tab-panel.active {
  display: grid;
}

/* ============ CARD ============ */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.card:hover {
  transform: translateY(-2px);
  box-shadow: 0 2px 6px rgba(20, 30, 60, 0.06), 0 16px 36px rgba(20, 30, 60, 0.08);
}

.card-header {
  padding: 20px 22px 8px;
}

.card-header h2 {
  margin: 0;
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.01em;
}

.card-header .desc {
  margin: 6px 0 0;
  color: var(--text-muted);
  font-size: 0.92rem;
}

.card-header em {
  font-style: normal;
  background: var(--primary-soft);
  color: var(--primary-dark);
  padding: 1px 6px;
  border-radius: 4px;
  font-weight: 600;
}

.card-header code {
  background: #f2f4f9;
  border: 1px solid var(--border);
  padding: 1px 6px;
  border-radius: 4px;
  font-size: 0.85em;
}

.card-body {
  padding: 12px 22px 22px;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

/* ============ FORM ============ */
.calc-form {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(130px, 1fr));
  gap: 12px;
}

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

.field label {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-muted);
  letter-spacing: 0.01em;
}

.field input {
  font-family: inherit;
  font-size: 1rem;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: #fafbfd;
  color: var(--text);
  transition: border-color 0.15s ease, box-shadow 0.15s ease, background 0.15s ease;
  width: 100%;
}

.field input:focus {
  outline: none;
  border-color: var(--primary);
  background: #fff;
  box-shadow: 0 0 0 3px rgba(45, 91, 255, 0.15);
}

.field input.invalid {
  border-color: var(--danger);
  background: #fdf3f4;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  background: var(--primary);
  color: #fff;
  border: none;
  padding: 11px 18px;
  font-family: inherit;
  font-size: 0.98rem;
  font-weight: 600;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: background 0.15s ease, transform 0.05s ease;
  align-self: flex-start;
}

.btn:hover {
  background: var(--primary-dark);
}

.btn:active {
  transform: translateY(1px);
}

/* ============ RESULT ============ */
.result {
  background: #f6f8fe;
  border: 1px solid #dae2f8;
  border-left: 4px solid var(--primary);
  border-radius: var(--radius-sm);
  padding: 14px 16px;
  font-size: 0.95rem;
  color: var(--text);
  animation: fadeIn 0.2s ease;
}

.result.error {
  background: #fdf3f4;
  border-color: #f3cdd2;
  border-left-color: var(--danger);
  color: #7a1a26;
}

.result .primary-result {
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--primary-dark);
  margin: 0 0 6px;
  letter-spacing: -0.01em;
}

.result.error .primary-result {
  color: var(--danger);
}

.result .details {
  margin: 6px 0 0;
  color: var(--text-muted);
  font-size: 0.88rem;
}

.result .details li {
  margin: 3px 0;
}

.result .formula {
  display: inline-block;
  background: #fff;
  border: 1px solid var(--border);
  padding: 3px 8px;
  border-radius: 4px;
  font-family: "SFMono-Regular", ui-monospace, Menlo, Consolas, monospace;
  font-size: 0.85rem;
  color: var(--text);
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(-4px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ============ NOTES ============ */
.notes {
  padding: 8px 20px 32px;
}

.notes details {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0;
  box-shadow: var(--shadow);
  overflow: hidden;
}

.notes summary {
  padding: 16px 22px;
  font-weight: 600;
  cursor: pointer;
  list-style: none;
  position: relative;
  color: var(--text);
}

.notes summary::-webkit-details-marker {
  display: none;
}

.notes summary::after {
  content: "+";
  position: absolute;
  right: 22px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 1.4rem;
  color: var(--primary);
  transition: transform 0.2s ease;
}

.notes details[open] summary::after {
  content: "−";
}

.notes ul {
  margin: 0;
  padding: 0 22px 20px 42px;
  color: var(--text-muted);
}

.notes li {
  margin: 6px 0;
}

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

/* ============ FOOTER ============ */
.site-footer {
  padding: 20px 0 32px;
  color: var(--text-muted);
  font-size: 0.88rem;
  text-align: center;
}

.site-footer p {
  margin: 4px 0;
}

.site-footer a {
  color: var(--primary);
  text-decoration: none;
  font-weight: 500;
}

.site-footer a:hover {
  text-decoration: underline;
}

/* ============ PAGE LÉGALE ============ */
.legal {
  padding: 32px 20px 48px;
}

.breadcrumb {
  margin-bottom: 24px;
  font-size: 0.92rem;
}

.breadcrumb a {
  color: var(--primary);
  text-decoration: none;
  font-weight: 500;
}

.breadcrumb a:hover {
  text-decoration: underline;
}

.legal-content {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 40px clamp(20px, 4vw, 56px);
  max-width: 820px;
  margin: 0 auto;
  line-height: 1.65;
  color: var(--text);
}

.legal-content h1 {
  margin: 0 0 8px;
  font-size: clamp(1.6rem, 3vw, 2.1rem);
  letter-spacing: -0.01em;
  color: var(--text);
}

.legal-content .updated {
  color: var(--text-muted);
  margin: 0 0 28px;
  font-size: 0.92rem;
}

.legal-content h2 {
  margin: 36px 0 12px;
  font-size: 1.18rem;
  color: var(--primary-dark);
  letter-spacing: -0.005em;
  padding-bottom: 6px;
  border-bottom: 1px solid var(--border);
}

.legal-content p {
  margin: 0 0 14px;
}

.legal-content ul {
  margin: 8px 0 18px;
  padding-left: 24px;
}

.legal-content li {
  margin: 4px 0;
}

.legal-content a {
  color: var(--primary);
  text-decoration: underline;
  text-underline-offset: 2px;
  word-break: break-word;
}

.legal-content a:hover {
  color: var(--primary-dark);
}

.legal-content strong {
  color: var(--text);
}

.legal-content .back-link {
  margin-top: 40px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
  text-align: center;
}

.legal-content .back-link a {
  text-decoration: none;
  font-weight: 600;
}

.legal-content .back-link a:hover {
  text-decoration: underline;
}

.about-list {
  margin: 16px 0 24px;
  padding: 20px 24px;
  background: #f6f8fe;
  border: 1px solid #dae2f8;
  border-radius: var(--radius-sm);
  display: grid;
  grid-template-columns: max-content 1fr;
  gap: 12px 24px;
  align-items: baseline;
}

.about-list dt {
  font-weight: 600;
  color: var(--primary-dark);
  font-size: 0.92rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

.about-list dd {
  margin: 0;
  color: var(--text);
}

.about-list dd a {
  color: var(--primary);
  text-decoration: underline;
  text-underline-offset: 2px;
}

@media (max-width: 520px) {
  .about-list {
    grid-template-columns: 1fr;
    gap: 4px 0;
  }
  .about-list dt {
    margin-top: 10px;
  }
  .about-list dt:first-child {
    margin-top: 0;
  }
}

/* ============ PAGE CALCULATEUR DÉDIÉE ============ */
.calculator-page {
  padding: 28px 20px 48px;
  max-width: 820px;
}

.calculator-page .breadcrumb {
  margin-bottom: 20px;
  font-size: 0.9rem;
  color: var(--text-muted);
}

.calculator-page .breadcrumb a {
  color: var(--primary);
  text-decoration: none;
  font-weight: 500;
}

.calculator-page .breadcrumb a:hover {
  text-decoration: underline;
}

.calculator-page .breadcrumb [aria-current="page"] {
  color: var(--text-muted);
}

.page-intro {
  margin-bottom: 24px;
}

.page-intro h1 {
  margin: 0 0 10px;
  font-size: clamp(1.7rem, 3.2vw, 2.3rem);
  letter-spacing: -0.015em;
  color: var(--text);
  line-height: 1.2;
}

.page-intro .lead {
  margin: 0;
  font-size: 1.08rem;
  color: var(--text-muted);
  line-height: 1.55;
}

.calc-standalone {
  margin: 0 0 40px;
}

/* Lien "Page dédiée →" sur la page d'accueil */
.card-dedicated {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  margin-top: 8px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--primary);
  text-decoration: none;
  padding: 4px 10px;
  background: var(--primary-soft);
  border-radius: 999px;
  transition: background 0.15s ease, color 0.15s ease;
  align-self: flex-start;
}

.card-dedicated:hover {
  background: var(--primary);
  color: #fff;
}

/* Contenu explicatif */
.explain {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 32px clamp(22px, 4vw, 40px);
  line-height: 1.65;
  color: var(--text);
  margin-bottom: 32px;
}

.explain h2 {
  margin: 32px 0 12px;
  font-size: 1.25rem;
  color: var(--primary-dark);
  letter-spacing: -0.005em;
  padding-bottom: 6px;
  border-bottom: 1px solid var(--border);
}

.explain h2:first-child {
  margin-top: 0;
}

.explain h3 {
  margin: 20px 0 8px;
  font-size: 1.05rem;
  color: var(--text);
}

.explain p {
  margin: 0 0 14px;
}

.explain ul,
.explain ol {
  margin: 8px 0 18px;
  padding-left: 24px;
}

.explain li {
  margin: 4px 0;
}

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

.explain code {
  background: #f2f4f9;
  border: 1px solid var(--border);
  padding: 1px 6px;
  border-radius: 4px;
  font-family: "SFMono-Regular", ui-monospace, Menlo, Consolas, monospace;
  font-size: 0.9em;
}

.formula-block {
  background: #f6f8fe;
  border: 1px solid #dae2f8;
  border-left: 4px solid var(--primary);
  padding: 14px 18px;
  border-radius: var(--radius-sm);
  margin: 10px 0 18px;
  font-size: 1rem;
  color: var(--text);
}

.formula-block code {
  background: transparent;
  border: none;
  padding: 0;
  font-size: 1em;
  color: var(--primary-dark);
  font-weight: 600;
}

.example-block {
  background: #f9faff;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 16px 18px;
  margin: 10px 0 18px;
}

.example-block p:last-child {
  margin-bottom: 0;
}

/* FAQ */
.faq details {
  background: #fafbfd;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0;
  margin-bottom: 10px;
  overflow: hidden;
}

.faq summary {
  padding: 14px 18px;
  font-weight: 600;
  cursor: pointer;
  list-style: none;
  position: relative;
  color: var(--text);
  padding-right: 44px;
}

.faq summary::-webkit-details-marker {
  display: none;
}

.faq summary::after {
  content: "+";
  position: absolute;
  right: 18px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 1.3rem;
  color: var(--primary);
  font-weight: 400;
  line-height: 1;
}

.faq details[open] summary::after {
  content: "−";
}

.faq details[open] summary {
  border-bottom: 1px solid var(--border);
}

.faq details > *:not(summary) {
  padding: 14px 18px;
  margin: 0;
  color: var(--text-muted);
}

.faq details p {
  margin: 0 0 8px;
}

.faq details p:last-child {
  margin-bottom: 0;
}

/* Calculateurs liés */
.related {
  margin-top: 32px;
}

.related h2 {
  margin: 0 0 16px;
  font-size: 1.2rem;
  color: var(--text);
}

.related-grid {
  list-style: none;
  padding: 0;
  margin: 0;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 12px;
}

.related-grid a {
  display: block;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 14px 16px;
  color: var(--text);
  text-decoration: none;
  font-weight: 500;
  transition: border-color 0.15s ease, transform 0.1s ease, box-shadow 0.15s ease;
  position: relative;
  padding-right: 32px;
}

.related-grid a::after {
  content: "→";
  position: absolute;
  right: 14px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--primary);
  transition: transform 0.15s ease;
}

.related-grid a:hover {
  border-color: var(--primary);
  box-shadow: 0 4px 12px rgba(45, 91, 255, 0.1);
}

.related-grid a:hover::after {
  transform: translateY(-50%) translateX(3px);
}

/* ============ RESPONSIVE ============ */
@media (max-width: 640px) {
  .site-header {
    padding: 32px 0 56px;
  }
  .logo {
    gap: 10px;
  }
  .logo-mark {
    width: 40px;
    height: 40px;
    font-size: 1.3rem;
  }
  .tab {
    padding: 8px 14px;
    font-size: 0.9rem;
  }
  .card-header,
  .card-body {
    padding-left: 18px;
    padding-right: 18px;
  }
  .tab-panel {
    grid-template-columns: 1fr;
  }
}