/* ==========================================================================
   Les Maths de Nadine — design system
   Aesthetic direction: "carnet de maths" — a warm, hand-touched notebook.
   Cream paper, ink borders, offset shadows, sticker-like tilts, generous
   typography (Fraunces display / Karla body). Each chapter owns one accent.
   ========================================================================== */

:root {
  --paper: #faf5ec;
  --paper-deep: #f3ecdd;
  --card: #fffdf7;
  --ink: #22303c;
  --ink-soft: #5d6b78;
  --ink-faint: #93a1ad;
  --line: #22303c;

  /* chapter accents */
  --c1: #0f8b8d; /* ensembles de nombres — sarcelle */
  --c2: #2e63e7; /* fonctions du 1er degré — bleu */
  --c3: #e0522e; /* fonctions du 2e degré — corail */
  --c4: #1f8a5b; /* fonctions polynomiales — vert */
  --c5: #7a4fbf; /* fonctions rationnelles — violet */
  --c6: #c77a0a; /* trigonométrie — ambre */
  --c7: #c2417a; /* puissances et racines — magenta */
  --c8: #3d4f91; /* systèmes linéaires — indigo */

  --tip: #c77a0a; /* amber used for tip/warning UI, independent of any chapter's accent */

  --good: #1f8a5b;
  --bad: #d64545;

  --accent: var(--c1);

  --radius: 18px;
  --shadow: 7px 7px 0 rgba(34, 48, 60, 0.14);
  --shadow-small: 4px 4px 0 rgba(34, 48, 60, 0.12);

  --font-display: "Fraunces", Georgia, "Times New Roman", serif;
  --font-body: "Karla", "Segoe UI", "Helvetica Neue", sans-serif;
}

/* ------------------------------------------------------------------ base */

* { box-sizing: border-box; }

/* Recalcule sur chaque element : declare une seule fois sur :root, la valeur
   serait figee avec l'accent de :root (bleu) et heritee telle quelle par les
   chapitres 2 a 5. */
* { --accent-soft: color-mix(in srgb, var(--accent, var(--c1)) 12%, var(--card)); }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background-color: var(--paper);
  background-image:
    radial-gradient(rgba(34, 48, 60, 0.055) 1px, transparent 1.4px);
  background-size: 26px 26px;
  color: var(--ink);
  font-family: var(--font-body);
  font-size: 1.12rem;
  line-height: 1.75;
}

::selection { background: var(--accent, var(--c1)); color: #fff; }

h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 700;
  line-height: 1.2;
  color: var(--ink);
}

h1 { font-size: clamp(2.2rem, 5vw, 3.4rem); letter-spacing: -0.01em; }
h2 {
  font-size: clamp(1.6rem, 3.2vw, 2.1rem);
  margin: 3.2rem 0 1.1rem;
  padding-left: 0.85rem;
  border-left: 8px solid var(--accent, var(--c1));
}
h3 { font-size: 1.3rem; margin: 2rem 0 0.6rem; }

p { margin: 0.9rem 0; max-width: 70ch; }

a { color: var(--accent); }

strong { font-weight: 800; }

img, canvas { max-width: 100%; }

/* ---------------------------------------------------------------- layout */

.wrap { max-width: 1060px; margin: 0 auto; padding: 0 1.4rem; }

/* -------------------------------------------------------------- top bar */

.topbar {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(250, 245, 236, 0.92);
  backdrop-filter: blur(8px);
  border-bottom: 2.5px solid var(--ink);
}

.topbar-inner {
  max-width: 1060px;
  margin: 0 auto;
  padding: 0.55rem 1.4rem;
  display: flex;
  align-items: center;
  gap: 0.6rem;
  flex-wrap: nowrap;
}

.brand {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1.25rem;
  color: var(--ink);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 0.55rem;
  margin-right: auto;
}

.brand .brand-mark {
  display: inline-grid;
  place-items: center;
  width: 2rem; height: 2rem;
  background: var(--accent, var(--c1));
  color: #fff;
  border: 2px solid var(--ink);
  border-radius: 9px;
  box-shadow: 3px 3px 0 rgba(34, 48, 60, 0.25);
  font-size: 1.05rem;
  transform: rotate(-4deg);
}

.topnav { display: flex; gap: 0.1rem; flex-wrap: wrap; }

#auth-status {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.88rem;
  white-space: nowrap;
  flex: none;
  margin-left: 0.6rem;
}
.auth-email { color: var(--ink-soft); font-weight: 700; }
.auth-link {
  font: inherit;
  font-weight: 800;
  color: var(--accent, var(--c1));
  background: none;
  border: none;
  cursor: pointer;
  text-decoration: none;
  padding: 0;
}
.auth-link:hover { text-decoration: underline; }

.topnav a {
  text-decoration: none;
  color: var(--ink-soft);
  font-weight: 700;
  font-size: 0.8rem;
  padding: 0.3rem 0.42rem;
  border-radius: 999px;
  border: 2px solid transparent;
  transition: all 0.15s ease;
}

.topnav a:hover { color: var(--ink); border-color: var(--ink); background: var(--card); }
.topnav a.active { color: #fff; background: var(--accent, var(--c1)); border-color: var(--ink); }

/* ----------------------------------------------------------------- hero */

.hero { padding: 4.5rem 0 2.5rem; position: relative; }

.hero .kicker {
  display: inline-block;
  font-weight: 800;
  font-size: 0.85rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent, var(--c1));
  background: var(--accent-soft);
  border: 2px solid var(--accent);
  border-radius: 999px;
  padding: 0.25rem 0.9rem;
  transform: rotate(-1.5deg);
}

.hero h1 { margin: 1rem 0 0.6rem; }
.hero h1 em {
  font-style: italic;
  color: var(--accent);
}

.hero .lead {
  font-size: 1.3rem;
  color: var(--ink-soft);
  max-width: 56ch;
}

/* chapter hero variant */
.chapter-hero { padding: 3.5rem 0 1.5rem; }
.chapter-hero .chap-num {
  font-family: var(--font-display);
  font-size: clamp(4rem, 12vw, 8rem);
  font-weight: 900;
  color: transparent;
  -webkit-text-stroke: 2.5px var(--accent);
  line-height: 1;
  float: right;
  transform: rotate(3deg);
  user-select: none;
}

/* ------------------------------------------------------- chapter cards  */

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(290px, 1fr));
  gap: 1.6rem;
  margin: 2.5rem 0;
}

.chapter-card {
  --accent: var(--c1);
  display: block;
  text-decoration: none;
  color: var(--ink);
  background: var(--card);
  border: 2.5px solid var(--ink);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1.5rem 1.5rem 1.3rem;
  position: relative;
  transition: transform 0.18s ease, box-shadow 0.18s ease;
}

.chapter-card:nth-child(odd) { transform: rotate(-0.7deg); }
.chapter-card:nth-child(even) { transform: rotate(0.7deg); }
.chapter-card:hover {
  transform: rotate(0deg) translateY(-5px);
  box-shadow: 10px 12px 0 rgba(34, 48, 60, 0.16);
}

.chapter-card .num {
  font-family: var(--font-display);
  font-weight: 900;
  font-size: 2.6rem;
  color: var(--accent);
  line-height: 1;
}

.chapter-card h3 { margin: 0.4rem 0 0.5rem; font-size: 1.45rem; }
.chapter-card p { color: var(--ink-soft); font-size: 1rem; margin: 0; }

.chapter-card .go {
  display: inline-block;
  margin-top: 0.9rem;
  font-weight: 800;
  color: var(--accent, var(--c1));
}

.chapter-card .done-badge {
  position: absolute;
  top: -12px; right: -10px;
  background: var(--good);
  color: #fff;
  font-weight: 800;
  font-size: 0.8rem;
  padding: 0.3rem 0.7rem;
  border: 2px solid var(--ink);
  border-radius: 999px;
  transform: rotate(6deg);
  display: none;
}
.chapter-card.is-done .done-badge { display: block; }

/* ----------------------------------------------------------------- boxes */

.box {
  background: var(--card);
  border: 2.5px solid var(--ink);
  border-radius: var(--radius);
  box-shadow: var(--shadow-small);
  padding: 1.1rem 1.4rem;
  margin: 1.4rem 0;
  position: relative;
}

.box .box-tag {
  position: absolute;
  top: -14px; left: 18px;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 0.9rem;
  padding: 0.15rem 0.8rem;
  border: 2px solid var(--ink);
  border-radius: 999px;
  background: var(--accent, var(--c1));
  color: #fff;
  transform: rotate(-1.5deg);
}

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

/* .box-def keeps the page accent — do NOT redeclare --accent here: a
   self-reference (--accent: var(--accent)) is cyclic, so the property becomes
   invalid at computed-value time and every var(--accent) below it resolves to
   nothing — which is how the "Définition" pill lost its background. */
.box-key     { background: color-mix(in srgb, var(--accent) 9%, var(--card)); }
.box-key .box-tag { background: var(--ink); }
.box-warn    { background: #fdeeee; }
.box-warn .box-tag { background: var(--bad); }
.box-example { background: #f4f8ff; border-style: dashed; }
.box-example .box-tag { background: #2e63e7; }
.box-tip     { background: #fdf6e4; }
.box-tip .box-tag { background: var(--tip); }

/* ------------------------------------------------------------- formulas */

.math {
  font-family: var(--font-display);
  font-size: 1.12em;
  font-weight: 500;
  white-space: nowrap;
}

.math-display {
  display: block;
  text-align: center;
  font-size: 1.3em;
  margin: 1rem 0;
  overflow-x: auto;
  padding: 0.4rem 0;
}

.frac {
  display: inline-flex;
  flex-direction: column;
  vertical-align: middle;
  text-align: center;
  margin: 0 0.15em;
  line-height: 1.25;
}
.frac > .num { border-bottom: 2px solid currentColor; padding: 0 0.4em; }
.frac > .den { padding: 0 0.4em; }

.sqrt { white-space: nowrap; }
.sqrt::before { content: "√"; }
.sqrt > span { border-top: 2px solid currentColor; padding: 0 0.15em; }

/* ------------------------------------------------------------- widgets */

.widget {
  background: var(--card);
  border: 2.5px solid var(--ink);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  margin: 2rem 0;
  overflow: hidden;
}

.widget-head {
  display: flex;
  align-items: center;
  gap: 0.7rem;
  padding: 0.8rem 1.3rem;
  border-bottom: 2.5px solid var(--ink);
  background: var(--accent-soft);
}

.widget-head .play-badge {
  background: var(--accent, var(--c1));
  color: #fff;
  font-weight: 800;
  font-size: 0.78rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  border: 2px solid var(--ink);
  border-radius: 999px;
  padding: 0.15rem 0.7rem;
}

.widget-head h3 { margin: 0; font-size: 1.15rem; }

.widget-body { padding: 1.2rem 1.3rem 1.4rem; }

.widget canvas.plot {
  display: block;
  width: 100%;
  background: #fffefa;
  border: 2px solid var(--ink);
  border-radius: 12px;
}
.widget canvas.plot:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--accent) 40%, transparent);
  outline-offset: 2px;
}

.widget .controls {
  display: flex;
  flex-wrap: wrap;
  gap: 1.2rem 2rem;
  margin-top: 1.1rem;
}

.slider {
  flex: 1 1 220px;
  min-width: 200px;
}

.slider label {
  display: flex;
  justify-content: space-between;
  font-weight: 800;
  font-size: 0.98rem;
  margin-bottom: 0.15rem;
}

.slider label output { color: var(--accent); font-family: var(--font-display); }

input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 10px;
  background: var(--paper-deep);
  border: 2px solid var(--ink);
  border-radius: 999px;
  outline: none;
  cursor: pointer;
}
input[type="range"]:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--accent) 40%, transparent);
  outline-offset: 2px;
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 24px; height: 24px;
  background: var(--accent, var(--c1));
  border: 2.5px solid var(--ink);
  border-radius: 50%;
  box-shadow: 2px 2px 0 rgba(34, 48, 60, 0.3);
  cursor: grab;
}
input[type="range"]::-moz-range-thumb {
  width: 20px; height: 20px;
  background: var(--accent, var(--c1));
  border: 2.5px solid var(--ink);
  border-radius: 50%;
  box-shadow: 2px 2px 0 rgba(34, 48, 60, 0.3);
  cursor: grab;
}

.widget .readout {
  margin-top: 1rem;
  background: var(--paper);
  border: 2px dashed var(--ink);
  border-radius: 12px;
  padding: 0.7rem 1rem;
  font-family: var(--font-display);
  font-size: 1.08em;
}

/* ------------------------------------------------------------- buttons */

.btn {
  display: inline-block;
  font-family: var(--font-body);
  font-weight: 800;
  font-size: 1rem;
  color: #fff;
  background: var(--accent, var(--c1));
  border: 2.5px solid var(--ink);
  border-radius: 12px;
  box-shadow: var(--shadow-small);
  padding: 0.55rem 1.3rem;
  cursor: pointer;
  transition: transform 0.12s ease, box-shadow 0.12s ease;
  text-decoration: none;
}

.btn:hover { transform: translateY(-2px); box-shadow: 6px 7px 0 rgba(34, 48, 60, 0.14); }
.btn:active { transform: translateY(2px); box-shadow: 2px 2px 0 rgba(34, 48, 60, 0.2); }

.btn.ghost { background: var(--card); color: var(--ink); }

/* ----------------------------------------------------------------- quiz */

.quiz {
  background: var(--card);
  border: 2.5px solid var(--ink);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  margin: 2.2rem 0;
  padding: 1.6rem 1.6rem 1.2rem;
  position: relative;
}

.quiz .box-tag {
  position: absolute;
  top: -14px; left: 18px;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 0.9rem;
  padding: 0.15rem 0.8rem;
  border: 2px solid var(--ink);
  border-radius: 999px;
  background: var(--good);
  color: #fff;
  transform: rotate(-1.5deg);
}

.quiz-q { margin-bottom: 1.5rem; padding-bottom: 1.3rem; border-bottom: 2px dashed var(--ink-faint); }
.quiz-q:last-of-type { border-bottom: none; }
.quiz-q .q-text { font-weight: 700; margin-bottom: 0.6rem; }

.quiz-q .choices { display: flex; flex-direction: column; gap: 0.45rem; }

.quiz-q .choice {
  text-align: left;
  font-family: var(--font-body);
  font-size: 1.02rem;
  background: var(--paper);
  border: 2px solid var(--ink);
  border-radius: 10px;
  padding: 0.5rem 0.9rem;
  cursor: pointer;
  transition: background 0.12s ease;
}
.quiz-q .choice:hover { background: var(--accent-soft); }
.quiz-q .choice.correct { background: #e2f4e9; border-color: var(--good); }
.quiz-q .choice.wrong { background: #fdeeee; border-color: var(--bad); }
.quiz-q .choice:disabled { cursor: default; opacity: 0.85; }
.quiz-q .choice:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--accent) 40%, transparent);
  outline-offset: 2px;
}

.quiz-q input.q-input {
  font-family: var(--font-display);
  font-size: 1.1rem;
  padding: 0.45rem 0.8rem;
  border: 2.5px solid var(--ink);
  border-radius: 10px;
  background: var(--paper);
  width: 10rem;
}
.quiz-q input.q-input:focus { outline: 3px solid color-mix(in srgb, var(--accent) 40%, transparent); }

.quiz-q .feedback { margin-top: 0.55rem; font-size: 0.98rem; display: none; }
.quiz-q .feedback.show { display: block; }
.quiz-q .feedback.good { color: var(--good); }
.quiz-q .feedback.bad { color: var(--bad); }
.quiz-q .feedback .explain { color: var(--ink-soft); display: block; margin-top: 0.2rem; }

.quiz-score {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1.2rem;
  text-align: center;
  margin-top: 1rem;
  display: none;
}
.quiz-score.show { display: block; }

/* --------------------------------------------------------- mini chapter nav */

.chap-toc {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin: 1.5rem 0 0;
}
.chap-toc a {
  text-decoration: none;
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--ink-soft);
  background: var(--card);
  border: 2px solid var(--ink-faint);
  border-radius: 999px;
  padding: 0.25rem 0.85rem;
  transition: all 0.15s ease;
}
.chap-toc a:hover { color: var(--ink); border-color: var(--ink); transform: translateY(-2px); }

/* chapter footer navigation */
.chap-nav {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  margin: 4rem 0 3rem;
  flex-wrap: wrap;
}

/* ------------------------------------------------------------ utilities */

.reveal { opacity: 0; transform: translateY(18px); transition: opacity 0.5s ease, transform 0.5s ease; }
.reveal.visible { opacity: 1; transform: none; }

.center { text-align: center; }
.mt-2 { margin-top: 2rem; }

footer.site-footer {
  border-top: 2.5px solid var(--ink);
  margin-top: 4rem;
  padding: 2rem 0 3rem;
  color: var(--ink-soft);
  font-size: 0.95rem;
  text-align: center;
}

/* ==========================================================================
   Part 2 — reading aids, interactive components, polish
   ========================================================================== */

/* ------------------------------------------------- reading progress bar */

.read-progress {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: 4px;
  z-index: 60;
  pointer-events: none;
  background: transparent;
}
.read-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent, var(--c1)), color-mix(in srgb, var(--accent, var(--c1)) 45%, var(--tip)));
  transform: scaleX(0);
  transform-origin: 0 50%;
  transition: transform 0.08s linear;
}

/* --------------------------------------------------------- back to top */

.to-top {
  position: fixed;
  right: 1.2rem;
  bottom: 1.2rem;
  z-index: 55;
  width: 3rem; height: 3rem;
  display: grid;
  place-items: center;
  font-size: 1.3rem;
  font-weight: 800;
  color: var(--ink);
  background: var(--card);
  border: 2.5px solid var(--ink);
  border-radius: 50%;
  box-shadow: var(--shadow-small);
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(12px);
  transition: opacity 0.2s ease, transform 0.2s ease, visibility 0.2s;
}
.to-top.show { opacity: 1; visibility: visible; transform: none; }
.to-top:hover { background: var(--accent, var(--c1)); color: #fff; }

/* ------------------------------------------------------- compagnon IA */

.compagnon-bouton {
  position: fixed;
  left: 1.2rem;
  bottom: 1.2rem;
  z-index: 55;
  font-family: var(--font-body);
  font-weight: 800;
  font-size: 0.95rem;
  color: var(--ink);
  background: var(--card);
  border: 2.5px solid var(--ink);
  border-radius: 999px;
  padding: 0.7rem 1.1rem;
  box-shadow: var(--shadow-small);
  cursor: pointer;
}
.compagnon-bouton:hover { background: var(--accent, var(--c1)); color: #fff; }

.compagnon-panneau {
  position: fixed;
  left: 1.2rem;
  bottom: 4.6rem;
  z-index: 56;
  width: min(22rem, calc(100vw - 2.4rem));
  max-height: min(28rem, calc(100vh - 7rem));
  max-height: min(28rem, calc(100dvh - 7rem));
  display: flex;
  flex-direction: column;
  background: var(--card);
  border: 2.5px solid var(--ink);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity 0.18s ease, transform 0.18s ease, visibility 0.18s;
}
.compagnon-panneau.open { opacity: 1; visibility: visible; transform: none; }

.compagnon-entete {
  display: flex; align-items: center; justify-content: space-between;
  padding: 0.7rem 1rem;
  border-bottom: 2.5px solid var(--ink);
  font-family: var(--font-display);
  font-weight: 700;
}
.compagnon-fermer {
  border: none; background: none; cursor: pointer;
  font-size: 1.1rem; color: var(--ink-soft); line-height: 1;
  padding: 0.2rem 0.3rem;
}
.compagnon-fermer:hover { color: var(--bad); }

.compagnon-messages {
  flex: 1 1 auto;
  overflow-y: auto;
  padding: 0.8rem 1rem;
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
  min-height: 3rem;
}
.compagnon-msg {
  font-size: 0.95rem;
  padding: 0.5rem 0.75rem;
  border-radius: 12px;
  border: 2px solid var(--ink);
  max-width: 90%;
  white-space: pre-wrap;
}
.compagnon-user { align-self: flex-end; background: var(--accent-soft); }
.compagnon-bot { align-self: flex-start; background: var(--paper); }
.compagnon-attente {
  color: var(--ink-faint);
  display: flex; align-items: center; gap: 0.6rem;
}
.compagnon-erreur { border-color: var(--bad); color: var(--bad); background: #fdeeee; }

.compagnon-points { display: inline-flex; gap: 0.22rem; }
.compagnon-points span {
  width: 6px; height: 6px; border-radius: 50%;
  background: var(--ink-faint);
  animation: compagnon-pulse 1.1s ease-in-out infinite;
}
.compagnon-points span:nth-child(2) { animation-delay: 0.15s; }
.compagnon-points span:nth-child(3) { animation-delay: 0.3s; }
@keyframes compagnon-pulse {
  0%, 80%, 100% { opacity: 0.25; transform: scale(0.8); }
  40% { opacity: 1; transform: scale(1); }
}
@media (prefers-reduced-motion: reduce) {
  .compagnon-points span { animation: none; opacity: 0.7; }
}

.compagnon-annuler, .compagnon-retry {
  border: none; background: none; cursor: pointer;
  font-size: 0.82rem; font-weight: 700;
  color: var(--ink-soft);
  text-decoration: underline;
  padding: 0;
}
.compagnon-retry { margin-left: 0.4rem; color: var(--bad); }
.compagnon-annuler:hover, .compagnon-retry:hover { color: var(--ink); }

.compagnon-ligne {
  display: flex; gap: 0.5rem; align-items: flex-end;
  padding: 0.7rem 1rem; border-top: 2px dashed var(--ink-faint);
}
.compagnon-input {
  flex: 1 1 auto;
  font-family: var(--font-body);
  font-size: 0.95rem;
  padding: 0.45rem 0.7rem;
  border: 2px solid var(--ink);
  border-radius: 10px;
  background: var(--paper);
  resize: none;
}
.compagnon-input:focus { outline: 3px solid color-mix(in srgb, var(--accent) 40%, transparent); }

@media (max-width: 640px) {
  .compagnon-bouton { left: 0.8rem; bottom: 0.8rem; padding: 0.6rem 0.9rem; font-size: 0.88rem; }
  .compagnon-panneau {
    left: 0.8rem; bottom: 4rem; width: calc(100vw - 1.6rem);
    max-height: min(28rem, calc(100vh - 5rem));
    max-height: min(28rem, calc(100dvh - 5rem));
  }
}

/* ---------------------------------------------------- nav refinements */

.topnav { overflow-x: auto; flex-wrap: nowrap; scrollbar-width: none; min-width: 0; }
.topnav::-webkit-scrollbar { display: none; }
.topnav a { white-space: nowrap; }

/* the chapter mini-menu sticks under the top bar while you read */
.chap-toc {
  position: sticky;
  top: var(--topbar-h, 51px);
  z-index: 40;
  margin: 1.5rem 0 0.5rem;
  padding: 0.55rem 0;
  background: rgba(250, 245, 236, 0.95);
  backdrop-filter: blur(6px);
  border-bottom: 2px solid transparent;
}
.chap-toc a.current {
  color: #fff;
  background: var(--accent, var(--c1));
  border-color: var(--ink);
  box-shadow: 2px 2px 0 rgba(34, 48, 60, 0.2);
}

/* --------------------------------------------------------- hero flair */

.hero { overflow: visible; }

/* An animated unit circle behind the hero heading — a point orbiting the
   ring with its sin/cos projections traced live, echoing the site's own
   "algèbre & trigonométrie" tagline. Markup built by initHeroCircle() in
   main.js; JS also owns the reduced-motion check (draws one still frame
   instead of animating) since the animation is JS-driven, not CSS. */
.hero-circle {
  position: absolute;
  top: 1.5rem; right: -2rem;
  width: 190px; height: 190px;
  z-index: -1;
  pointer-events: none;
}
.hero-circle svg { width: 100%; height: 100%; }
.hero-circle .ring {
  fill: none;
  stroke: color-mix(in srgb, var(--accent, var(--c1)) 35%, transparent);
  stroke-width: 3;
  stroke-dasharray: 8 7;
}
.hero-circle .axis {
  stroke: color-mix(in srgb, var(--accent, var(--c1)) 14%, transparent);
  stroke-width: 1;
}
.hero-circle .proj {
  stroke: color-mix(in srgb, var(--accent, var(--c1)) 55%, transparent);
  stroke-width: 1.5;
  stroke-dasharray: 3 3;
}
.hero-circle .radius {
  stroke: var(--accent, var(--c1));
  stroke-width: 1.5;
  opacity: 0.55;
}
.hero-circle .dot { fill: var(--accent, var(--c1)); }
.hero-circle .pi-label {
  font-family: var(--font-display);
  font-style: italic;
  font-size: 15px;
  fill: var(--ink-soft);
}

.hero-formulas {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  margin-top: 1.6rem;
}
.hero-formulas span {
  font-family: var(--font-display);
  font-size: 1.05rem;
  background: var(--card);
  border: 2px solid var(--ink);
  border-radius: 999px;
  padding: 0.2rem 0.9rem;
  box-shadow: 3px 3px 0 rgba(34, 48, 60, 0.1);
}
.hero-formulas span:nth-child(odd) { transform: rotate(-1.6deg); }
.hero-formulas span:nth-child(even) { transform: rotate(1.4deg); }

/* ------------------------------------------------ progress dashboard */

.prog-dash {
  display: flex;
  align-items: center;
  gap: 1.6rem;
  flex-wrap: wrap;
  background: var(--card);
  border: 2.5px solid var(--ink);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1.4rem 1.6rem;
  margin: 2rem 0;
}
.prog-ring { position: relative; width: 96px; height: 96px; flex: none; }
.prog-ring svg { width: 100%; height: 100%; transform: rotate(-90deg); }
.prog-ring circle { fill: none; stroke-width: 10; stroke-linecap: round; }
.prog-ring .ring-bg { stroke: var(--paper-deep); }
.prog-ring .ring-fg { stroke: var(--good); transition: stroke-dashoffset 0.8s ease; }
.prog-ring span {
  position: absolute; inset: 0;
  display: grid; place-items: center;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1.25rem;
}
.prog-text { flex: 1 1 260px; }
.prog-text h3 { margin: 0 0 0.3rem; }
.prog-text p { margin: 0 0 0.7rem; color: var(--ink-soft); }
.prog-ex-stat, .prog-streak, .prog-exam { font-weight: 700; color: var(--ink); }

.chapter-card .quiz-badge {
  display: none;
  margin-top: 0.6rem;
  font-size: 0.85rem;
  font-weight: 800;
  color: var(--good);
  background: color-mix(in srgb, var(--good) 12%, var(--card));
  border: 2px solid var(--good);
  border-radius: 999px;
  padding: 0.1rem 0.7rem;
  width: fit-content;
}
.chapter-card .quiz-badge.show { display: block; }

/* ----------------------------------------------------------- StepBox */

.steps { display: flex; flex-direction: column; gap: 0.2rem; }

.step {
  display: flex;
  gap: 0.9rem;
  align-items: flex-start;
  padding: 0.55rem 0.2rem;
  border-bottom: 2px dashed color-mix(in srgb, var(--ink-faint) 55%, transparent);
}
.step:last-child { border-bottom: none; }

.step-index {
  flex: none;
  display: grid; place-items: center;
  width: 1.9rem; height: 1.9rem;
  margin-top: 0.35rem;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 0.95rem;
  color: #fff;
  background: var(--accent, var(--c1));
  border: 2px solid var(--ink);
  border-radius: 50%;
}
.step-body { flex: 1 1 auto; min-width: 0; }
.step-math { text-align: left; margin: 0.1rem 0 0.2rem; }
.step-note { margin: 0; color: var(--ink-soft); font-size: 0.95rem; max-width: none; }
.step-new { animation: step-in 0.32s ease; }
@keyframes step-in {
  from { opacity: 0; transform: translateY(-8px); }
  to { opacity: 1; transform: none; }
}

.steps-bar {
  display: flex;
  align-items: center;
  gap: 0.9rem;
  flex-wrap: wrap;
  margin-top: 1rem;
}
.steps-dots { display: flex; gap: 0.35rem; margin: 0 auto; }
.steps-dots .dot {
  width: 10px; height: 10px;
  border-radius: 50%;
  border: 2px solid var(--ink-faint);
  background: transparent;
  transition: background 0.2s ease, border-color 0.2s ease;
}
.steps-dots .dot.on { background: var(--accent, var(--c1)); border-color: var(--ink); }

/* -------------------------------------------------------- sign table */

.signtable-wrap { overflow-x: auto; margin: 1.2rem 0 0.6rem; -webkit-overflow-scrolling: touch; }

.signtable {
  border-collapse: collapse;
  overflow: hidden;
  width: 100%;
  min-width: 420px;
  background: var(--card);
  font-family: var(--font-display);
  border: 2.5px solid var(--ink);
  border-radius: 10px;
}
.signtable tr + tr { border-top: 2px solid var(--ink); }
.signtable tr:first-child { background: var(--accent-soft); }
.signtable th, .signtable td { padding: 0.45rem 0.3rem; text-align: center; }

.signtable .st-head {
  text-align: left;
  padding-left: 0.9rem;
  white-space: nowrap;
  border-right: 2.5px solid var(--ink);
  font-weight: 700;
  background: color-mix(in srgb, var(--paper) 70%, var(--card));
}
.signtable .st-product { background: color-mix(in srgb, var(--accent) 10%, var(--card)); }
.signtable .st-product .st-head { font-weight: 800; background: color-mix(in srgb, var(--accent) 16%, var(--card)); }

.signtable .st-root { font-weight: 800; white-space: nowrap; }
.signtable .st-bound { color: var(--ink-soft); font-size: 0.9em; padding: 0 0.4rem; }
.signtable .st-zero { width: 1.6rem; }
.signtable .st-sign { min-width: 3.2rem; }

.signtable .sg { font-size: 1.15em; font-weight: 800; }
.signtable .sg.pos { color: var(--good); }
.signtable .sg.neg { color: var(--bad); }
.signtable .sg.zero { color: var(--ink); }
.signtable .sg.bar {
  color: var(--bad);
  font-size: 1.3em;
  letter-spacing: -0.05em;
}

.st-query { margin-top: 1rem; }
.st-buttons { display: flex; gap: 0.5rem; flex-wrap: wrap; }
.st-answer { font-size: 1.05em; }

/* geometry canvases keep a sane aspect instead of stretching very wide */
.widget canvas.plot.square { max-width: 560px; margin-left: auto; margin-right: auto; }

/* ---------------------------------------------- polynomial long division */

.polydiv {
  font-family: "SF Mono", "JetBrains Mono", "Fira Mono", ui-monospace, monospace;
  font-size: 0.94rem;
  line-height: 1.6;
  background: var(--paper);
  border: 2px dashed var(--ink);
  border-radius: 12px;
  padding: 1rem 1.1rem;
  margin: 1rem 0 0;
  overflow-x: auto;
  white-space: pre;
  tab-size: 4;
}

/* legend under a graphic */
.legend { display: flex; gap: 1.1rem; flex-wrap: wrap; margin-top: 0.8rem; font-size: 0.95rem; color: var(--ink-soft); }
.legend span { display: inline-flex; align-items: center; gap: 0.4rem; }
.legend i {
  width: 18px; height: 5px; border-radius: 3px; display: inline-block;
  background: currentColor;
}

/* ------------------------------------------------------ value tables */

.vtable-wrap { overflow-x: auto; margin: 1.3rem 0; }
.vtable {
  border-collapse: collapse;
  width: 100%;
  min-width: 380px;
  background: var(--card);
  border: 2.5px solid var(--ink);
  border-radius: 10px;
  font-family: var(--font-display);
}
.vtable th, .vtable td {
  padding: 0.5rem 0.8rem;
  text-align: center;
  border: 1.5px solid color-mix(in srgb, var(--ink) 30%, transparent);
}
.vtable thead th { background: var(--accent, var(--c1)); color: #fff; font-weight: 800; border-color: var(--ink); }
.vtable tbody tr:nth-child(even) { background: color-mix(in srgb, var(--accent) 6%, var(--card)); }
.vtable tbody th { background: color-mix(in srgb, var(--paper) 70%, var(--card)); font-weight: 800; }

/* ------------------------------------------------------ small layout */

.grid-2 {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.2rem;
  margin: 1.4rem 0;
}

.btn.small { font-size: 0.9rem; padding: 0.35rem 0.9rem; border-radius: 10px; }

.chips { display: flex; gap: 0.5rem; flex-wrap: wrap; margin-top: 1rem; }

.num-input {
  font-family: var(--font-display);
  font-size: 1.05rem;
  width: 5.5rem;
  padding: 0.3rem 0.55rem;
  border: 2px solid var(--ink);
  border-radius: 8px;
  background: var(--paper);
  color: inherit;
}
.field-row { display: flex; gap: 0.9rem; flex-wrap: wrap; align-items: center; margin-top: 0.9rem; }
.field-row label { font-weight: 800; display: inline-flex; align-items: center; gap: 0.35rem; }

/* --------------------------------------------------------- quiz extras */

.quiz-meter {
  height: 8px;
  background: var(--paper-deep);
  border: 2px solid var(--ink);
  border-radius: 999px;
  overflow: hidden;
  margin: 0.4rem 0 1.4rem;
}
.quiz-meter-fill {
  height: 100%;
  width: 0;
  background: var(--good);
  transition: width 0.35s ease;
}

.quiz-q .q-row { display: flex; gap: 0.6rem; align-items: center; flex-wrap: wrap; }
.quiz-q input.q-input.ok { border-color: var(--good); background: #e2f4e9; }
.quiz-q input.q-input.ko { border-color: var(--bad); background: #fdeeee; }

/* ---------------------------------------------------------- confetti */

.confetti {
  position: fixed;
  width: 9px; height: 14px;
  border-radius: 2px;
  pointer-events: none;
  z-index: 999;
  animation: confetti-fly 1.4s cubic-bezier(0.2, 0.7, 0.4, 1) forwards;
}
@keyframes confetti-fly {
  0% { opacity: 1; transform: translate(0, 0) rotate(0deg); }
  100% { opacity: 0; transform: translate(var(--dx), calc(var(--dy) + 320px)) rotate(var(--rot)); }
}


/* ==========================================================================
   Banque d'exercices
   ========================================================================== */

.exo-filtres { margin: 1.6rem 0 1rem; display: flex; flex-direction: column; gap: 0.55rem; }
.filtre { display: flex; gap: 0.45rem; flex-wrap: wrap; }
.filtre .btn.on { background: var(--accent, var(--c1)); color: #fff; }

.exo-barre {
  display: flex; align-items: center; gap: 1rem; flex-wrap: wrap;
  justify-content: space-between;
  padding: 0.6rem 0 1rem;
  border-bottom: 2px dashed var(--ink-faint);
  color: var(--ink-soft);
}
.exo-barre .btn.on { background: var(--accent, var(--c1)); color: #fff; border-color: var(--ink); }

.exo {
  background: var(--card);
  border: 2.5px solid var(--ink);
  border-left: 9px solid var(--accent, var(--c1));
  border-radius: var(--radius);
  box-shadow: var(--shadow-small);
  padding: 1.1rem 1.3rem 1.2rem;
  margin: 1.3rem 0;
}
.exo-ok { background: color-mix(in srgb, var(--good) 7%, var(--card)); }
.exo-revoir { background: #fdf6e4; }

.exo-head {
  display: flex; align-items: center; gap: 0.6rem; flex-wrap: wrap;
  margin-bottom: 0.7rem;
}
.exo-id {
  font-family: var(--font-display); font-weight: 800; font-size: 0.85rem;
  color: #fff; background: var(--accent, var(--c1));
  border: 2px solid var(--ink); border-radius: 999px; padding: 0.1rem 0.7rem;
}
.exo-sec { font-weight: 700; color: var(--ink-soft); font-size: 0.92rem; }
.exo-level { margin-left: auto; color: var(--accent, var(--c1)); font-size: 0.9rem; letter-spacing: 0.1em; }
.exo-level-txt { color: var(--ink-faint); letter-spacing: 0; font-size: 0.85rem; }
.exo-marque { font-weight: 800; font-size: 0.85rem; color: var(--good); }
.exo-revoir .exo-marque { color: var(--tip); }

.exo-parts-badge { display: flex; gap: 0.3rem; font-size: 0.82rem; font-weight: 800; }
.exo-parts-badge span { padding: 0.05rem 0.4rem; border-radius: 999px; border: 1.5px solid var(--ink-faint); color: var(--ink-soft); }
.exo-parts-badge .part-ok { border-color: var(--good); color: var(--good); background: color-mix(in srgb, var(--good) 10%, var(--card)); }
.exo-parts-badge .part-ko { border-color: var(--bad); color: var(--bad); background: color-mix(in srgb, var(--bad) 10%, var(--card)); }

.exo-q { margin-bottom: 0.9rem; }
.exo-q .math { white-space: normal; }

.exo-saisie { display: flex; gap: 0.6rem; align-items: center; flex-wrap: wrap; margin-bottom: 0.9rem; }
.exo-saisie .q-input { width: 13rem; }
.exo-part-label { font-weight: 800; color: var(--accent); }
.exo-champ-expr { display: inline-flex; }
.exo-champ-expr .q-input { width: 13rem; }
.q-mathfield { width: 13rem; font-size: 1.05rem; border: 2.5px solid var(--ink); border-radius: 10px; padding: 0.2rem 0.5rem; background: var(--paper); }
.exo-fb { font-weight: 800; font-size: 0.95rem; }
.exo-fb.good { color: var(--good); }
.exo-fb.bad { color: var(--bad); }

.exo-qcm { display: flex; flex-direction: column; gap: 0.45rem; margin-bottom: 0.9rem; }
.exo-qcm .choice {
  text-align: left;
  font-family: var(--font-body);
  font-size: 1.02rem;
  background: var(--paper);
  border: 2px solid var(--ink);
  border-radius: 10px;
  padding: 0.5rem 0.9rem;
  cursor: pointer;
  transition: background 0.12s ease;
}
.exo-qcm .choice:hover { background: var(--accent-soft); }
.exo-qcm .choice.correct { background: #e2f4e9; border-color: var(--good); }
.exo-qcm .choice.wrong { background: #fdeeee; border-color: var(--bad); }
.exo-qcm .choice.selected { border-width: 3px; }
/* En mode examen (examen.js), .selected est posé SEUL (pas de .correct/.wrong,
   la correction est différée) : sans ce style le clic est presque invisible —
   un simple épaississement de bordure sur un cadre déjà foncé. */
.exo-qcm .choice.selected:not(.correct):not(.wrong) { background: var(--accent, var(--c1)); color: #fff; border-color: var(--ink); }
.exo-qcm .choice:disabled { cursor: default; opacity: 0.85; }
.exo-qcm .choice:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--accent) 40%, transparent);
  outline-offset: 2px;
}

.exo-actions { display: flex; gap: 0.5rem; flex-wrap: wrap; }

.exo-indice:empty { display: none; }
.exo-indice p {
  background: #fdf6e4;
  border: 2px dashed var(--ink-faint);
  border-radius: 10px;
  padding: 0.55rem 0.85rem;
  margin: 0.6rem 0 0;
  font-size: 0.95rem;
}

.exo-session-note {
  display: none;
  margin: 0 0 1rem;
  padding: 0.7rem 1rem;
  background: color-mix(in srgb, var(--accent) 9%, var(--card));
  border: 2px dashed var(--ink-faint);
  border-radius: 10px;
  font-size: 0.95rem;
  color: var(--ink-soft);
}
.exo-session-note.show { display: block; }
.exo-taille-session { display: none; margin: 0 0 1rem; }
.exo-taille-session.show { display: flex; }
.exo-vide { color: var(--ink-soft); font-style: italic; padding: 1rem 0; }

.exo-correction {
  display: none;
  margin-top: 1.1rem;
  padding-top: 0.8rem;
  border-top: 2px dashed var(--ink-faint);
}
.exo-correction.open { display: block; animation: step-in 0.28s ease; }
.exo-res { margin-top: 1rem; }

/* ============================================================ Examen blanc */

.examen-barre {
  display: flex; align-items: center; justify-content: space-between;
  flex-wrap: wrap; gap: 0.8rem;
  padding: 0.9rem 1.1rem;
  margin-bottom: 1.4rem;
  background: var(--card);
  border: 2.5px solid var(--ink);
  border-radius: var(--radius);
  box-shadow: var(--shadow-small);
  position: sticky;
  top: var(--topbar-h, 51px);
  z-index: 40;
}
.examen-chrono {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1.3rem;
  font-variant-numeric: tabular-nums;
  color: var(--accent);
}

.examen-score {
  text-align: center;
  background: var(--card);
  border: 2.5px solid var(--ink);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1.6rem;
  margin-bottom: 1.4rem;
}
.examen-score h2 { margin: 0 0 0.4rem; border: none; padding: 0; font-size: 2.4rem; }
.examen-score p { color: var(--ink-soft); margin: 0; }

.examen-parchap {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 0.7rem;
  margin-bottom: 1rem;
}
.examen-parchap-row {
  display: flex; justify-content: space-between; align-items: center;
  background: var(--card);
  border: 2px solid var(--ink);
  border-left: 7px solid var(--accent, var(--c1));
  border-radius: 10px;
  padding: 0.5rem 0.9rem;
  font-variant-numeric: tabular-nums;
}

@media print {
  .topbar, .compagnon-bouton, .compagnon-panneau, .to-top, .read-progress,
  .site-footer, .chap-nav, .exo-actions, .btn { display: none !important; }
  body { background: #fff; }
  .exo { break-inside: avoid; box-shadow: none; }
}

/* ----------------------------------------------------------- mobile */

@media (max-width: 640px) {
  body { font-size: 1.05rem; }
  .chapter-hero .chap-num { float: none; display: block; font-size: 4rem; }
  .wrap { padding: 0 1rem; }
  .brand { font-size: 1.05rem; }
  .brand span.brand-label { display: none; }
  h2 { margin-top: 2.4rem; }
  .widget-body { padding: 1rem 0.9rem 1.2rem; }
  .box { padding: 1rem 1rem; }
  .hero-circle { display: none; }
  .to-top { right: 0.8rem; bottom: 0.8rem; width: 2.6rem; height: 2.6rem; }
  .prog-dash { padding: 1.1rem; gap: 1.1rem; }
  .exo { padding: 1rem; border-left-width: 7px; }
  .exo-level { margin-left: 0; width: 100%; }
  .exo-saisie .q-input { width: 100%; }
  /* the mini-menu scrolls sideways instead of eating half the screen */
  .chap-toc {
    flex-wrap: nowrap;
    overflow-x: auto;
    scrollbar-width: none;
    margin-left: -1rem;
    margin-right: -1rem;
    padding-left: 1rem;
    padding-right: 1rem;
  }
  .chap-toc::-webkit-scrollbar { display: none; }
  .chap-toc a { white-space: nowrap; }
}

/* --------------------------------------------------------- tablet tier */

@media (min-width: 641px) and (max-width: 1024px) {
  .widget .controls { gap: 0.9rem 1.2rem; }
  .slider { flex: 1 1 45%; min-width: 160px; }
  .widget canvas.plot.square { max-width: 420px; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .reveal { transition: none; opacity: 1; transform: none; }
  .chapter-card, .chapter-card:hover { transform: none; }
  .step-new { animation: none; }
}