/* ============================================================
   Machine Learning — Comprendre, réviser, réussir
   Design system global
   ============================================================ */

:root {
  /* Palette */
  --navy:        #1B2A4A;
  --navy-soft:   #24365C;
  --blue:        #2E5A9C;
  --blue-light:  #4A7BC8;
  --teal:        #3AAFA9;
  --teal-dark:   #2A8A85;

  --bg:          #F8FAFC;
  --bg-alt:      #EEF2F7;
  --surface:     #FFFFFF;
  --surface-2:   #F1F5F9;

  --text:        #1A2233;
  --text-soft:   #4A5568;
  --text-mute:   #718096;
  --border:      #D9E1EC;
  --border-soft: #E8EEF6;

  /* Callouts */
  --intuition-bg:  #EAF2FB;
  --intuition-brd: #2E5A9C;
  --def-bg:        #E8F5E9;
  --def-brd:       #2E7D32;
  --example-bg:    #F5F9FF;
  --example-brd:   #4A7BC8;
  --warn-bg:       #FFF3E0;
  --warn-brd:      #E65100;
  --math-bg:       #F3F4F6;
  --math-brd:      #6B7280;
  --exam-bg:       #E0F2FE;
  --exam-brd:      #0284C7;
  --key-bg:        #FFFDE7;
  --key-brd:       #CA8A04;

  /* Typography */
  --font-serif: Georgia, "Iowan Old Style", "Palatino Linotype", "Times New Roman", serif;
  --font-sans:  -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono:  "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;

  /* Layout */
  --content-width: 780px;
  --sidebar-width: 280px;
  --radius: 10px;
  --radius-sm: 6px;
  --shadow-sm: 0 1px 2px rgba(15,23,42,0.06);
  --shadow:    0 4px 12px rgba(15,23,42,0.08);
  --shadow-lg: 0 12px 32px rgba(15,23,42,0.12);
}

/* ---------- Reset ---------- */
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-serif);
  font-size: 17px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

img, svg { max-width: 100%; height: auto; }

a {
  color: var(--blue);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color 0.15s ease, color 0.15s ease;
}
a:hover { border-bottom-color: var(--blue); }

/* ---------- Layout ---------- */
.layout {
  display: grid;
  grid-template-columns: var(--sidebar-width) 1fr;
  min-height: 100vh;
}

.sidebar {
  background: var(--navy);
  color: #E8EEF6;
  padding: 24px 20px 40px;
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
  font-family: var(--font-sans);
}

.sidebar__brand {
  display: block;
  color: #FFFFFF;
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: 0.2px;
  margin-bottom: 4px;
  border: none;
}
.sidebar__brand:hover { border: none; }
.sidebar__tag {
  display: block;
  color: #94A9C9;
  font-size: 0.78rem;
  margin-bottom: 24px;
}

.sidebar h3 {
  color: #B7C6DE;
  font-size: 0.72rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  margin: 22px 0 8px;
  border: none;
  padding: 0;
}

.sidebar nav a {
  display: block;
  color: #DDE7F5;
  font-size: 0.9rem;
  padding: 6px 10px;
  border-radius: var(--radius-sm);
  border: none;
  margin: 1px 0;
}
.sidebar nav a:hover {
  background: var(--navy-soft);
  color: #FFFFFF;
  border: none;
}
.sidebar nav a.active {
  background: var(--blue);
  color: #FFFFFF;
  font-weight: 600;
}
.sidebar nav a .done {
  color: var(--teal);
  font-weight: 700;
  margin-right: 4px;
}

.sidebar__progress {
  margin-top: 24px;
  padding-top: 20px;
  border-top: 1px solid rgba(255,255,255,0.1);
}
.sidebar__progress-label {
  font-size: 0.75rem;
  color: #94A9C9;
  margin-bottom: 6px;
}
.sidebar__progress-bar {
  height: 6px;
  background: rgba(255,255,255,0.1);
  border-radius: 3px;
  overflow: hidden;
}
.sidebar__progress-fill {
  height: 100%;
  background: var(--teal);
  width: 0%;
  transition: width 0.3s ease;
}

.main {
  min-width: 0;
  display: flex;
  flex-direction: column;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(248,250,252,0.95);
  backdrop-filter: blur(6px);
  border-bottom: 1px solid var(--border-soft);
  padding: 12px 32px;
  display: flex;
  align-items: center;
  gap: 16px;
  font-family: var(--font-sans);
}
.topbar__menu {
  display: none;
  background: none;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 1.2rem;
  padding: 2px 10px;
  cursor: pointer;
  color: var(--navy);
}
.topbar__search {
  flex: 1;
  max-width: 420px;
  position: relative;
}
.topbar__search input {
  width: 100%;
  padding: 8px 12px 8px 34px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-family: inherit;
  font-size: 0.9rem;
  background: var(--surface);
  color: var(--text);
}
.topbar__search input:focus {
  outline: none;
  border-color: var(--blue);
  box-shadow: 0 0 0 3px rgba(46,90,156,0.12);
}
.topbar__search::before {
  content: "🔍";
  position: absolute;
  left: 10px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 0.85rem;
  opacity: 0.5;
}
.topbar__results {
  position: absolute;
  top: 100%;
  left: 0;
  right: 0;
  margin-top: 6px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-lg);
  max-height: 320px;
  overflow-y: auto;
  display: none;
  z-index: 100;
}
.topbar__results.open { display: block; }
.topbar__results a {
  display: block;
  padding: 10px 14px;
  font-size: 0.88rem;
  border: none;
  color: var(--text);
  border-bottom: 1px solid var(--border-soft);
}
.topbar__results a:last-child { border-bottom: none; }
.topbar__results a:hover {
  background: var(--bg-alt);
  border: none;
}
.topbar__results small {
  display: block;
  color: var(--text-mute);
  font-size: 0.75rem;
}

/* ---------- Content ---------- */
.content {
  max-width: var(--content-width);
  width: 100%;
  padding: 40px 32px 80px;
  margin: 0 auto;
}

.breadcrumb {
  font-family: var(--font-sans);
  font-size: 0.82rem;
  color: var(--text-mute);
  margin-bottom: 16px;
}
.breadcrumb a { color: var(--text-mute); }
.breadcrumb a:hover { color: var(--blue); border-bottom-color: var(--blue); }

h1, h2, h3, h4, h5 {
  font-family: var(--font-sans);
  color: var(--navy);
  line-height: 1.3;
  margin-top: 1.6em;
  margin-bottom: 0.6em;
}
h1 {
  font-size: 2rem;
  margin-top: 0;
  padding-bottom: 12px;
  border-bottom: 3px solid var(--teal);
}
h2 { font-size: 1.45rem; }
h3 { font-size: 1.15rem; }
h4 { font-size: 1rem; color: var(--blue); }

p { margin: 0 0 1em; }

ul, ol { padding-left: 1.4em; margin: 0 0 1em; }
li { margin-bottom: 0.3em; }

code {
  font-family: var(--font-mono);
  font-size: 0.88em;
  background: var(--bg-alt);
  padding: 2px 6px;
  border-radius: 4px;
  color: var(--navy-soft);
}

strong { color: var(--navy); }

/* ---------- Tables ---------- */
table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.2em 0;
  font-family: var(--font-sans);
  font-size: 0.9rem;
  background: var(--surface);
  border-radius: var(--radius-sm);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}
thead {
  background: var(--navy);
  color: #FFFFFF;
}
th, td {
  padding: 10px 14px;
  text-align: left;
  border-bottom: 1px solid var(--border-soft);
  vertical-align: top;
}
th { font-weight: 600; font-size: 0.85rem; }
tbody tr:hover { background: var(--bg-alt); }
tbody tr:last-child td { border-bottom: none; }
caption {
  caption-side: bottom;
  padding: 8px 4px;
  font-size: 0.82rem;
  color: var(--text-mute);
  text-align: left;
  font-style: italic;
}

/* ---------- Callouts ---------- */
.callout {
  margin: 1.4em 0;
  padding: 16px 20px;
  border-left: 4px solid;
  border-radius: var(--radius-sm);
  background: var(--surface);
  font-size: 0.96em;
}
.callout__title {
  display: block;
  font-family: var(--font-sans);
  font-weight: 700;
  font-size: 0.82rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 8px;
}
.callout p:last-child { margin-bottom: 0; }

.callout--intuition { background: var(--intuition-bg); border-color: var(--intuition-brd); }
.callout--intuition .callout__title { color: var(--intuition-brd); }

.callout--def { background: var(--def-bg); border-color: var(--def-brd); }
.callout--def .callout__title { color: var(--def-brd); }

.callout--example { background: var(--example-bg); border-color: var(--example-brd); }
.callout--example .callout__title { color: var(--example-brd); }

.callout--warn { background: var(--warn-bg); border-color: var(--warn-brd); }
.callout--warn .callout__title { color: var(--warn-brd); }

.callout--math { background: var(--math-bg); border-color: var(--math-brd); }
.callout--math .callout__title { color: var(--math-brd); }

.callout--exam { background: var(--exam-bg); border-color: var(--exam-brd); }
.callout--exam .callout__title { color: var(--exam-brd); }

.callout--key { background: var(--key-bg); border-color: var(--key-brd); }
.callout--key .callout__title { color: var(--key-brd); }

/* ---------- Math ---------- */
.math-block {
  display: block;
  margin: 1.2em 0;
  padding: 14px 18px;
  background: var(--surface);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius-sm);
  overflow-x: auto;
  text-align: center;
  font-size: 1.05em;
}
.math-inline {
  font-family: var(--font-serif);
  font-style: italic;
}
math { font-size: 1.05em; }

/* ---------- Source ref ---------- */
.src {
  display: inline-block;
  font-family: var(--font-sans);
  font-size: 0.72rem;
  color: var(--text-mute);
  background: var(--bg-alt);
  border-radius: 4px;
  padding: 1px 7px;
  margin-left: 4px;
  vertical-align: middle;
  white-space: nowrap;
}

/* ---------- Progress / checklist ---------- */
.progress-row {
  display: flex;
  align-items: center;
  gap: 12px;
  margin: 10px 0;
  font-family: var(--font-sans);
  font-size: 0.9rem;
}
.progress-row__check {
  width: 18px; height: 18px;
  border: 2px solid var(--border);
  border-radius: 4px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  background: var(--surface);
  color: transparent;
  font-size: 0.75rem;
  font-weight: 700;
}
.progress-row__check.done {
  background: var(--teal);
  border-color: var(--teal);
  color: #fff;
}
.progress-row a { flex: 1; }

/* ---------- Buttons ---------- */
.btn {
  display: inline-block;
  font-family: var(--font-sans);
  font-size: 0.88rem;
  font-weight: 600;
  padding: 8px 16px;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  cursor: pointer;
  background: var(--blue);
  color: #fff;
  transition: background 0.15s ease, transform 0.05s ease;
}
.btn:hover { background: var(--blue-light); }
.btn:active { transform: translateY(1px); }
.btn--ghost {
  background: transparent;
  color: var(--blue);
  border-color: var(--blue);
}
.btn--ghost:hover { background: var(--intuition-bg); }

/* ---------- Chapter navigation footer ---------- */
.chapter-nav {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
  font-family: var(--font-sans);
}
.chapter-nav a {
  padding: 10px 16px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--navy);
  font-size: 0.88rem;
}
.chapter-nav a:hover {
  border-color: var(--blue);
  color: var(--blue);
  border-bottom-color: var(--blue);
}
.chapter-nav__label {
  display: block;
  font-size: 0.72rem;
  color: var(--text-mute);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 2px;
}

/* ---------- Homepage ---------- */
.hero {
  background: linear-gradient(135deg, var(--navy) 0%, var(--blue) 100%);
  color: #fff;
  padding: 48px 40px;
  border-radius: var(--radius);
  margin-bottom: 32px;
  box-shadow: var(--shadow-lg);
}
.hero h1 {
  color: #fff;
  border: none;
  font-size: 2.2rem;
  margin: 0 0 8px;
  padding: 0;
}
.hero p {
  color: #DDE7F5;
  margin: 0 0 4px;
  font-size: 1.05rem;
}
.hero__meta {
  font-size: 0.85rem;
  color: #94A9C9;
  margin-top: 12px;
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 16px;
  margin: 20px 0 32px;
}
.card {
  display: block;
  background: var(--surface);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius);
  padding: 18px 20px;
  color: var(--text);
  border-bottom: 1px solid var(--border-soft);
  transition: border-color 0.15s ease, box-shadow 0.15s ease, transform 0.1s ease;
}
.card:hover {
  border-color: var(--blue);
  box-shadow: var(--shadow);
  transform: translateY(-2px);
  border-bottom-color: var(--blue);
}
.card__num {
  display: inline-block;
  font-family: var(--font-sans);
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--teal);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: 6px;
}
.card__title {
  font-family: var(--font-sans);
  font-size: 1rem;
  font-weight: 700;
  color: var(--navy);
  margin-bottom: 6px;
}
.card__desc {
  font-size: 0.85rem;
  color: var(--text-soft);
  line-height: 1.5;
}

.module-title {
  font-family: var(--font-sans);
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--teal-dark);
  margin: 32px 0 12px;
  padding-bottom: 6px;
  border-bottom: 1px solid var(--border);
}

/* ---------- Roadmap ---------- */
.roadmap {
  background: var(--surface);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius);
  padding: 24px;
  margin: 24px 0;
  overflow-x: auto;
}
.roadmap svg { min-width: 700px; }

/* ---------- Exercises ---------- */
.exercise {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 22px;
  margin: 18px 0;
}
.exercise__head {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 12px;
  margin-bottom: 10px;
  font-family: var(--font-sans);
}
.exercise__num {
  font-weight: 700;
  color: var(--blue);
  font-size: 0.9rem;
}
.exercise__tag {
  font-size: 0.72rem;
  color: var(--text-mute);
  background: var(--bg-alt);
  padding: 2px 8px;
  border-radius: 10px;
}
.answer {
  display: none;
  margin-top: 14px;
  padding: 14px 16px;
  background: var(--key-bg);
  border-left: 3px solid var(--key-brd);
  border-radius: var(--radius-sm);
  font-size: 0.93em;
}
.answer.open { display: block; }
.answer__toggle {
  margin-top: 10px;
}

/* ---------- Search results ---------- */
.search-result {
  display: block;
  padding: 10px 14px;
  border-bottom: 1px solid var(--border-soft);
  border-left: none;
  color: var(--text);
}
.search-result:last-child { border-bottom: none; }
.search-result:hover { background: var(--bg-alt); border-left: none; }
.search-result strong { color: var(--blue); }
.search-result small { display: block; color: var(--text-mute); font-size: 0.78rem; }

/* ---------- Mobile ---------- */
@media (max-width: 960px) {
  .layout { grid-template-columns: 1fr; }
  .sidebar {
    position: fixed;
    top: 0; left: 0; bottom: 0;
    width: 280px;
    transform: translateX(-100%);
    transition: transform 0.25s ease;
    z-index: 200;
  }
  .sidebar.open { transform: translateX(0); }
  .topbar__menu { display: inline-block; }
  .content { padding: 24px 20px 60px; }
  h1 { font-size: 1.6rem; }
  .hero { padding: 32px 24px; }
  .hero h1 { font-size: 1.6rem; }
}

@media (max-width: 600px) {
  body { font-size: 16px; }
  .topbar { padding: 10px 16px; }
  .content { padding: 20px 16px 60px; }
  .chapter-nav { flex-direction: column; }
  .chapter-nav a { text-align: center; }
  table { font-size: 0.82rem; }
  th, td { padding: 8px 10px; }
}

/* ---------- Overlay for mobile sidebar ---------- */
.overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(15,23,42,0.45);
  z-index: 150;
}
.overlay.open { display: block; }

/* ---------- Print ---------- */
@media print {
  .sidebar, .topbar, .chapter-nav, .overlay, .no-print { display: none !important; }
  body { background: #fff; font-size: 11pt; color: #000; }
  .layout { display: block; }
  .content { max-width: 100%; padding: 0; }
  .callout { break-inside: avoid; box-shadow: none; background: #fff !important; }
  table { break-inside: avoid; box-shadow: none; }
  h1 { border-bottom: 2px solid #000; }
  a { color: #000; border: none; }
  .math-block { background: #fff; border: none; padding: 8px 0; }
  .hero { background: #fff !important; color: #000; box-shadow: none; border: 1px solid #ccc; }
  .hero h1, .hero p { color: #000; }
}