:root {
  color-scheme: light dark;
  --primary: #4b6cb7;
  --secondary: #182848;
  --accent: #ff6b6b;
  --bg: #f5f7fa;
  --surface: #ffffff;
  --text: #2b2f36;
  --muted: #5d6573;
  --border: #dde3ee;
  --success: #1f9d57;
  --focus: #e08a00;
  --n6: #3498db;
  --n5: #2ecc71;
  --n4: #e74c3c;
  --n3: #f39c12;
  --radius: 12px;
  --shadow: 0 4px 14px rgba(24, 40, 72, .1);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #11151f;
    --surface: #1a2030;
    --text: #e8ecf4;
    --muted: #a3adc2;
    --border: #2c3550;
    --primary: #7f9cdc;
    --shadow: 0 4px 14px rgba(0, 0, 0, .4);
  }
}

:root[data-theme="light"] { color-scheme: light; }
:root[data-theme="dark"] {
  color-scheme: dark;
  --bg: #11151f;
  --surface: #1a2030;
  --text: #e8ecf4;
  --muted: #a3adc2;
  --border: #2c3550;
  --primary: #7f9cdc;
  --shadow: 0 4px 14px rgba(0, 0, 0, .4);
}
:root[data-theme="dark"] h1 { color: #fff; }
:root[data-theme="dark"] .tabs button[aria-selected="true"] { color: #11151f; }
:root[data-theme="dark"] .btn:not(.ghost) { color: #11151f; }

:root[data-size="l"] { font-size: 112.5%; }
:root[data-size="xl"] { font-size: 125%; }
:root[data-dys="1"] body { font-family: Verdana, "Trebuchet MS", Tahoma, sans-serif; letter-spacing: .04em; word-spacing: .16em; line-height: 1.9; }
:root[data-dys="1"] .frac, :root[data-dys="1"] .fig text { letter-spacing: 0; }

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: "Segoe UI", system-ui, -apple-system, Roboto, sans-serif;
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

a { color: var(--primary); }
:focus-visible { outline: 3px solid var(--focus); outline-offset: 2px; border-radius: 4px; }

.skip { position: absolute; left: -999px; top: 0; background: var(--surface); padding: .5rem 1rem; z-index: 10; }
.skip:focus { left: 8px; top: 8px; }

header.site {
  background: linear-gradient(135deg, #4b6cb7 0%, #182848 100%);
  color: #fff;
  padding: .9rem 16px;
  box-shadow: var(--shadow);
}
header.site .inner { max-width: 1200px; margin: 0 auto; display: flex; align-items: center; gap: 1rem; flex-wrap: wrap; }
.brand { display: flex; align-items: center; gap: .75rem; color: #fff; text-decoration: none; }
.brand img { width: 44px; height: 44px; display: block; }
.brand span { font-size: 1.5rem; font-weight: 700; letter-spacing: .01em; }
.brand small { display: block; font-size: .8rem; font-weight: 400; opacity: .85; margin-top: -.3rem; }
header.site nav { margin-left: auto; display: flex; gap: .5rem; flex-wrap: wrap; }
header.site nav a { color: #fff; text-decoration: none; padding: .35rem .8rem; border-radius: 999px; border: 1px solid rgba(255, 255, 255, .45); font-size: .95rem; }
header.site nav a:hover, header.site nav a[aria-current="true"] { background: rgba(255, 255, 255, .2); }

main { flex: 1; width: 100%; max-width: 1200px; margin: 0 auto; padding: 24px 16px 40px; }

h1 { color: var(--secondary); font-size: 2rem; margin: 0 0 .5rem; line-height: 1.25; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) h1 { color: #fff; } }

.lead { color: var(--muted); max-width: 70ch; margin: 0 0 1.5rem; }

.crumbs { font-size: .9rem; color: var(--muted); margin-bottom: 1rem; }
.crumbs a { color: var(--muted); }

.levels { display: grid; grid-template-columns: repeat(auto-fit, minmax(230px, 1fr)); gap: 1rem; }
.level-card {
  display: block; background: var(--surface); border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 1.25rem; text-decoration: none; color: var(--text); border-top: 6px solid var(--c);
  transition: transform .15s;
}
.level-card:hover { transform: translateY(-3px); }
.level-card .big { font-size: 2.6rem; font-weight: 800; color: var(--c); line-height: 1; }
.level-card h2 { margin: .4rem 0 .2rem; font-size: 1.15rem; }
.level-card p { margin: 0; color: var(--muted); font-size: .9rem; }

.tabs { display: flex; gap: .5rem; margin: 1rem 0; flex-wrap: wrap; }
.tabs button {
  font: inherit; cursor: pointer; padding: .5rem 1.1rem; border-radius: 999px;
  border: 2px solid var(--primary); background: var(--surface); color: var(--primary); font-weight: 600;
}
.tabs button[aria-selected="true"] { background: var(--primary); color: #fff; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) .tabs button[aria-selected="true"] { color: #11151f; } }

details.chap { background: var(--surface); border-radius: var(--radius); box-shadow: var(--shadow); margin-bottom: .75rem; border-left: 6px solid var(--c); }
details.chap > summary { cursor: pointer; padding: .9rem 1.1rem; font-weight: 700; font-size: 1.05rem; }

.serie h3 { font-size: .95rem; margin: 0 0 .3rem; color: var(--muted); text-transform: none; }
.serie ol { margin: 0; padding-left: 1.3rem; }
.serie li { margin: .15rem 0; }
.serie li a { text-decoration: none; }
.serie li a:hover { text-decoration: underline; }
.vu::after { content: " ✓"; color: var(--success); font-weight: 700; }

.exo-grid { display: grid; grid-template-columns: minmax(0, 1fr) 280px; gap: 1.5rem; align-items: start; }
@media (max-width: 860px) { .exo-grid { grid-template-columns: 1fr; } }

.player-box { background: var(--surface); border-radius: var(--radius); box-shadow: var(--shadow); padding: 1rem; }
.frame {
  --c: var(--primary);
  background: var(--surface); border: 1px solid var(--border); border-top: 6px solid var(--c);
  border-radius: var(--radius); overflow: hidden; transition: border-color .2s;
}
.frame.is-aide { --c: var(--accent); }
.frame-bar { display: flex; align-items: center; gap: .6rem; padding: .55rem .9rem; font-size: .85rem; }
.frame-bar .chip { background: var(--c); color: #fff; padding: .1rem .7rem; border-radius: 999px; font-weight: 700; }
.frame-bar .mode { font-weight: 600; color: var(--muted); }
.frame-bar .count { margin-left: auto; color: var(--muted); font-variant-numeric: tabular-nums; }
.steps { display: flex; gap: 6px; padding: .8rem .9rem 1rem; flex-wrap: wrap; justify-content: center; }
.step { width: 26px; height: 8px; border-radius: 999px; background: var(--border); }
.step.done { background: color-mix(in srgb, var(--c) 45%, var(--border)); }
.step.on { background: var(--c); width: 40px; }
.step:hover { background: var(--c); }


.controls { display: flex; gap: .5rem; flex-wrap: wrap; margin-top: .9rem; }
.btn {
  font: inherit; cursor: pointer; padding: .55rem 1.1rem; border-radius: 8px; border: 2px solid var(--primary);
  background: var(--primary); color: #fff; font-weight: 600; text-decoration: none;
}
.btn.ghost { background: transparent; color: var(--primary); }
.btn[aria-disabled="true"] { opacity: .45; pointer-events: none; }
.controls .spacer { flex: 1; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) .btn:not(.ghost) { color: #11151f; } }

aside.side { background: var(--surface); border-radius: var(--radius); box-shadow: var(--shadow); padding: 1rem; }
aside.side h2 { font-size: 1rem; margin: 0 0 .5rem; }
aside.side ol { margin: 0; padding-left: 1.3rem; }
aside.side li { margin: .25rem 0; }
aside.side a[aria-current="page"] { font-weight: 700; color: var(--accent); }

.legal { background: var(--surface); border-radius: var(--radius); box-shadow: var(--shadow); padding: 1.5rem; max-width: 80ch; }
.legal h2 { color: var(--primary); margin-top: 1.5rem; font-size: 1.2rem; }
.todo { background: #fff3cd; color: #5a4300; padding: 0 .3rem; border-radius: 4px; font-weight: 600; }

footer.site { background: var(--secondary); color: #d7deef; padding: 1.25rem 16px; font-size: .9rem; }
footer.site .inner { max-width: 1200px; margin: 0 auto; display: flex; gap: .5rem 1.5rem; flex-wrap: wrap; align-items: center; }
footer.site a { color: #fff; }
footer.site .grow { flex: 1; min-width: 240px; }

.notice { background: var(--surface); border-left: 6px solid var(--accent); padding: 1rem; border-radius: 8px; box-shadow: var(--shadow); }

@media (prefers-reduced-motion: reduce) { .level-card, .frame { transition: none; } }

/* ----- exercices ----- */
.exo-wrap { max-width: 820px; }
.qbody { padding: .4rem 1.1rem 1rem; }
.q { font-size: 1.15rem; margin-bottom: 1rem; }
.q p { margin: .4rem 0; }
.q b { color: var(--text); }
.muted { color: var(--muted); font-size: .9rem; }

.frac { display: inline-flex; flex-direction: column; align-items: center; vertical-align: middle; line-height: 1.15; margin: 0 .15em; font-size: .95em; }
.frac > span:first-child { border-bottom: 1.5px solid currentColor; padding: 0 .25em .05em; }
.frac > span:last-child { padding: .05em .25em 0; }
.tab { border-collapse: collapse; margin: .6rem 0; }
.tab th, .tab td { border: 1px solid var(--border); padding: .3rem .9rem; text-align: center; }
.tab th { background: color-mix(in srgb, var(--primary) 12%, transparent); text-align: left; }
.sys { display: inline-flex; flex-direction: column; border-left: 3px solid var(--primary); padding-left: .7rem; vertical-align: middle; margin-left: .3rem; }

.fig { display: block; max-width: 280px; width: 100%; height: auto; margin: .5rem 0; }
.fig line, .fig path, .fig polygon, .fig circle, .fig rect { stroke: var(--text); fill: none; stroke-width: 2; stroke-linecap: round; stroke-linejoin: round; }
.fig .fill { fill: color-mix(in srgb, var(--primary) 14%, transparent); }
.fig .acc { stroke: var(--accent); stroke-width: 2.5; }
.fig .grid { stroke: var(--border); stroke-width: 1; }
.fig .axis { stroke: var(--muted); stroke-width: 1.6; }
.fig .dot { fill: var(--accent); stroke: none; }
.fig text { fill: var(--text); font: 600 13px "Segoe UI", system-ui, sans-serif; }
.fig text.tick { font-size: 9px; fill: var(--muted); font-weight: 400; }
.fig text.lab { fill: var(--accent); }

.qform { display: grid; gap: .8rem; }
.field { display: flex; align-items: center; gap: .5rem; flex-wrap: wrap; }
.field .lab { font-weight: 600; min-width: 5.5rem; }
.ans {
  font: inherit; font-size: 1.1rem; padding: .5rem .8rem; width: 12rem; max-width: 100%; border-radius: 8px;
  border: 2px solid var(--border); background: var(--bg); color: var(--text);
}
.ans:focus { border-color: var(--primary); }
.ans[aria-invalid="true"] { border-color: var(--danger, #e74c3c); }
.ans[aria-invalid="false"] { border-color: var(--success); }
.sym { font: inherit; cursor: pointer; border: 2px solid var(--border); background: var(--surface); color: var(--text); border-radius: 8px; padding: .45rem .8rem; }
.unit { color: var(--muted); }

.choices { display: grid; gap: .5rem; }
.choice { display: flex; align-items: center; gap: .7rem; background: var(--bg); border: 2px solid var(--border); border-radius: 10px; padding: .65rem .9rem; cursor: pointer; }
.choice:has(input:checked) { border-color: var(--primary); background: color-mix(in srgb, var(--primary) 12%, transparent); }
.choice:has(input:focus-visible) { outline: 3px solid var(--focus); }
.choice input { accent-color: var(--primary); width: 1.1rem; height: 1.1rem; }

.fb { min-height: 1.5rem; padding: 0; border-radius: 8px; }
.fb:empty { display: none; }
.fb.good, .fb.bad, .fb.warn { padding: .75rem 1rem; border-left: 5px solid; }
.fb.good { background: color-mix(in srgb, var(--success) 14%, transparent); border-color: var(--success); }
.fb.bad { background: color-mix(in srgb, var(--accent) 14%, transparent); border-color: var(--accent); }
.fb.warn { background: color-mix(in srgb, var(--focus) 16%, transparent); border-color: var(--focus); }

.step.miss { background: var(--accent); }

.result .score { font-size: 3rem; font-weight: 800; color: var(--c); margin: .2rem 0; line-height: 1.1; }
.result .appr { font-size: 1.15rem; margin: 0 0 .3rem; }
.recap { list-style: none; padding: 0; margin: 1rem 0; display: grid; gap: .4rem; }
.recap li { display: flex; gap: .6rem; align-items: baseline; padding: .4rem .7rem; border-radius: 8px; background: var(--bg); font-size: .92rem; }
.recap .ic { font-weight: 800; }
.recap .ok .ic { color: var(--success); }
.recap .ko .ic { color: var(--accent); }

.cards { padding: 0 1.1rem 1rem; display: grid; grid-template-columns: repeat(auto-fill, minmax(250px, 1fr)); gap: .6rem; }
.serie-card { display: flex; justify-content: space-between; align-items: center; gap: .6rem; padding: .7rem .9rem; border: 2px solid var(--border); border-radius: 10px; text-decoration: none; color: var(--text); background: var(--bg); }
.serie-card:hover { border-color: var(--c); }
.serie-card .t { font-weight: 600; }
.badge { font-size: .8rem; padding: .1rem .6rem; border-radius: 999px; background: var(--border); color: var(--muted); white-space: nowrap; font-variant-numeric: tabular-nums; }
.badge.gold { background: var(--success); color: #fff; }

/* ----- leçons ----- */
.lesson-link { display: inline-block; margin: 0 1.1rem .8rem; font-weight: 600; color: var(--primary); }
.lesson { background: var(--surface); border-radius: var(--radius); box-shadow: var(--shadow); border-top: 6px solid var(--c); padding: 1.2rem 1.3rem 1.4rem; max-width: 80ch; }
.lesson .chip { background: var(--c); color: #fff; padding: .1rem .8rem; border-radius: 999px; font-weight: 700; font-size: .85rem; }
.lesson h2 { font-size: 1.15rem; margin: 1.4rem 0 .6rem; color: var(--primary); }
.rule { background: color-mix(in srgb, var(--c) 10%, transparent); border-left: 5px solid var(--c); border-radius: 8px; padding: .2rem 1rem .6rem; margin-top: 1rem; }
.rule h2 { margin-top: .8rem; }
.rule ul { margin: 0; padding-left: 1.2rem; display: grid; gap: .5rem; }
.ex { background: var(--bg); border-radius: 8px; padding: .6rem .9rem; margin-bottom: .6rem; }
.ex p { margin: .2rem 0; }
.exa > span:first-child { color: var(--success); font-weight: 700; }
.rule li.nobullet { list-style: none; margin-left: -1.2rem; }
.trap { border-left-color: var(--focus); margin: 1rem 0; }
.cards.flat { padding: 0; }
.lesson-nav { margin-top: 1rem; }

/* ----- évaluations et révision ----- */
.serie-card.eval { border-style: dashed; border-color: var(--c); }
.notice.rev { margin-top: 1.5rem; display: flex; gap: 1rem; align-items: center; flex-wrap: wrap; justify-content: space-between; }
.notice.rev p { margin: 0; flex: 1; min-width: 220px; }
.recap .rep { color: var(--muted); }
.recap .rep b { color: var(--text); }

/* ----- réglages d'affichage ----- */
.prefs-btn { font: inherit; font-size: .95rem; cursor: pointer; color: #fff; background: transparent; padding: .35rem .8rem; border-radius: 999px; border: 1px solid rgba(255, 255, 255, .45); }
.prefs-btn:hover, .prefs-btn[aria-expanded="true"] { background: rgba(255, 255, 255, .2); }
.prefs-panel { position: absolute; right: 0; top: calc(100% + .6rem); z-index: 20; width: min(320px, 92vw); background: var(--surface); color: var(--text); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow); padding: .8rem 1rem 1rem; }
.prefs-panel[hidden] { display: none; }
.prefs-panel fieldset { border: 0; padding: 0; margin: 0 0 .7rem; }
.prefs-panel legend { font-weight: 700; padding: 0; margin-bottom: .2rem; }
.prefs-panel label { display: block; padding: .15rem 0; cursor: pointer; }
.prefs-panel input { accent-color: var(--primary); }
.prefs-reset { font: inherit; cursor: pointer; border: 2px solid var(--border); background: transparent; color: var(--text); border-radius: 8px; padding: .3rem .8rem; }
@media print { header.site, footer.site, .controls, .prefs-btn { display: none !important; } }

.fig .axisym { stroke: var(--accent); stroke-width: 2; stroke-dasharray: 6 4; }
.fig .curve { stroke: var(--accent); stroke-width: 2.6; }

.cards.brevet-top { padding: 0 0 1rem; grid-template-columns: 1fr; }