/* L'exo du jour. The one strong element is the "copie": a French squared exam sheet (5 mm grid,
   red margin). Everything else stays plain. Colours are variables with a dark set; keep both in sync. */
:root {
  --paper: #f7f9fc;      /* page */
  --sheet: #ffffff;      /* the copie */
  --grid: #dbe5f2;       /* petits carreaux */
  --ink: #1b2433;        /* text */
  --muted: #5a6577;
  --line: #d5dce6;
  --pen: #1d3e8f;        /* fountain-pen blue: links, buttons */
  --on-pen: #ffffff;
  --red: #c8372d;        /* margin and teacher's correction ink */
  --ok: #26734a;
  --warn: #8a5a00;
  --focus: #1d3e8f;
  --serif: 'Literata', Georgia, serif;
  --sans: 'Atkinson Hyperlegible', system-ui, sans-serif;
  --cell: 20px;          /* ~5 mm on a phone */
  --margin: 56px;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper: #121a2b; --sheet: #172238; --grid: #24324c; --ink: #e7ecf5; --muted: #a3afc2; --line: #2e3c57;
    --pen: #9db8ff; --on-pen: #0f1830; --red: #ff8278; --ok: #6fcf97; --warn: #f2c230; --focus: #9db8ff; color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --paper: #121a2b; --sheet: #172238; --grid: #24324c; --ink: #e7ecf5; --muted: #a3afc2; --line: #2e3c57;
  --pen: #9db8ff; --on-pen: #0f1830; --red: #ff8278; --ok: #6fcf97; --warn: #f2c230; --focus: #9db8ff; color-scheme: dark;
}

/* Maths: STIX Two Math (SIL Open Font License, public/fonts/STIXTwoMath-OFL.txt), loaded only by pages with formulas. */
@font-face { font-family: 'STIX Two Math'; src: url('/fonts/STIXTwoMath.woff2') format('woff2'); font-display: swap; }

*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--paper); color: var(--ink); font: 400 1.0625rem/1.65 var(--serif); }
a { color: var(--pen); text-underline-offset: 3px; text-decoration-thickness: 1px; }
:focus-visible { outline: 3px solid var(--focus); outline-offset: 2px; }
.skip { position: absolute; inset-inline-start: 8px; top: -60px; background: var(--sheet); padding: 8px 12px; z-index: 2; }
.skip:focus { top: 8px; }

/* ---------------------------------------------------------------- frame */
.top, main, .foot { max-width: 44rem; margin-inline: auto; padding-inline: 16px; }
main.wide { max-width: 60rem; }
.top { display: flex; justify-content: space-between; align-items: center; gap: 16px; padding-block: 14px; font-family: var(--sans); }
.brand { font: 600 1.15rem/1.2 var(--serif); color: var(--ink); text-decoration: none; }
.top-nav { display: flex; gap: 4px; }
.top-nav a { display: inline-flex; align-items: center; min-height: 44px; padding-inline: 10px; text-decoration: none; color: var(--muted); }
.top-nav a[aria-current] { color: var(--ink); text-decoration: underline; text-decoration-color: var(--red); text-decoration-thickness: 2px; }
main { padding-block: 8px 56px; }
.foot { display: flex; gap: 20px; flex-wrap: wrap; padding-block: 24px 40px; border-top: 1px solid var(--line); font: .875rem var(--sans); }
.foot a { color: var(--muted); }

h1 { font: 600 1.75rem/1.2 var(--serif); margin: 0 0 12px; letter-spacing: -0.01em; }
h2 { font: 600 1.2rem/1.3 var(--serif); margin: 32px 0 10px; }
p { margin: 0 0 12px; }
.lead { font-size: 1.15rem; }
.muted { color: var(--muted); }
.small { font-size: .875rem; }
code { font-family: ui-monospace, Menlo, monospace; font-size: .95em; }
.narrow { max-width: 32rem; }
.prose { max-width: 38rem; }
.prose li { margin-bottom: 8px; }

/* ---------------------------------------------------------------- the copie */
.copie {
  position: relative;
  background-color: var(--sheet);
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: var(--cell) var(--cell);
  background-position: -1px -1px;
  border: 1px solid var(--line);
  border-radius: 2px;
  padding: calc(var(--cell) * 2) var(--cell) calc(var(--cell) * 1.5) calc(var(--margin) + var(--cell));
  margin-block: 8px 24px;
  line-height: calc(var(--cell) * 1.5);
}
.copie::before { /* the red margin line */
  content: ''; position: absolute; top: 0; bottom: 0; inset-inline-start: var(--margin);
  border-inline-start: 2px solid var(--red);
}
.copie > * { position: relative; }
.copie-date { font: 400 .9375rem/1.4 var(--sans); color: var(--muted); margin-bottom: var(--cell); }
.copie-date::first-letter { text-transform: uppercase; }
.copie h1 { font-size: clamp(2rem, 7vw, 2.75rem); margin-bottom: var(--cell); }
@media (max-width: 480px) {
  :root { --margin: 28px; }
  .copie { padding-inline: calc(var(--margin) + 12px) 12px; }
}

/* ---------------------------------------------------------------- lists and facts */
.level-list { list-style: none; margin: 0; padding: 0; border-top: 1px solid var(--line); font-family: var(--sans); }
.level-list li { display: flex; justify-content: space-between; align-items: center; min-height: 52px; border-bottom: 1px solid var(--line); font-size: 1.0625rem; }
.level-list a { flex: 1; display: flex; align-items: center; min-height: 52px; text-decoration: none; color: var(--ink); }
.facts { margin: 16px 0 24px; font-family: var(--sans); }
.facts div { display: grid; grid-template-columns: 9.5rem 1fr; gap: 12px; padding-block: 10px; border-bottom: 1px solid var(--line); }
.facts dt { color: var(--muted); }
.facts dd { margin: 0; overflow-wrap: anywhere; }
@media (max-width: 420px) { .facts div { grid-template-columns: 1fr; gap: 2px; } }
.tally { display: grid; grid-template-columns: repeat(auto-fit, minmax(9rem, 1fr)); gap: 0; margin: 16px 0 24px; border-top: 1px solid var(--line); font-family: var(--sans); }
.tally div { padding: 12px 4px; border-bottom: 1px solid var(--line); }
.tally dt { color: var(--muted); font-size: .875rem; }
.tally dd { margin: 0; font: 600 1.6rem/1.2 var(--serif); font-variant-numeric: tabular-nums; }

/* ---------------------------------------------------------------- forms */
.stack { display: grid; gap: 14px; justify-items: start; margin-block: 16px; }
.spaced { margin-top: 32px; }
label { font: 700 .9375rem var(--sans); }
label.check { display: flex; gap: 10px; align-items: center; font-weight: 400; min-height: 44px; }
input[type=checkbox] { width: 22px; height: 22px; accent-color: var(--pen); }
input, select, textarea { font: 400 1rem var(--sans); } /* >= 16 px: no zoom on iOS */
.btn { display: inline-flex; align-items: center; justify-content: center; min-height: 48px; padding: 0 20px; border-radius: 6px;
  border: 1px solid var(--pen); background: var(--pen); color: var(--on-pen); font: 700 1rem var(--sans); text-decoration: none; cursor: pointer; }
.btn.secondary { background: transparent; color: var(--pen); }
.btn.danger { background: var(--red); border-color: var(--red); color: #fff; }
.danger-zone { margin-top: 40px; font-family: var(--sans); }
.danger-zone summary { cursor: pointer; color: var(--red); min-height: 44px; display: flex; align-items: center; }
.flash { padding: 10px 14px; border-inline-start: 3px solid currentColor; background: var(--sheet); font-family: var(--sans); }
.flash.ok { color: var(--ok); }
.flash.err { color: var(--red); }
.flash.warn { color: var(--warn); }

/* ---------------------------------------------------------------- exercise content */
.exo-title { font: 600 clamp(1.6rem, 6vw, 2.25rem)/1.2 var(--serif); margin: 0 0 8px; }
.exo-title a { color: inherit; text-decoration: none; }
.exo-title a:hover { text-decoration: underline; }
.exo-meta { font: .9375rem/1.5 var(--sans); color: var(--muted); display: flex; flex-wrap: wrap; gap: 4px 8px; align-items: baseline; margin-bottom: var(--cell); }
.exo-meta a { color: var(--muted); }
.exo-facts { display: inline-flex; gap: 10px; margin-inline-start: auto; }
.diff { color: var(--pen); letter-spacing: 1px; font-size: .8rem; }
.rich { line-height: 1.65; }
.rich p:last-child { margin-bottom: 0; }
.rich img { max-width: 100%; height: auto; display: block; margin: 12px 0; background: #fff; border: 1px solid var(--line); }
.rich ul, .rich ol { padding-inline-start: 1.4em; }
.math-display { overflow-x: auto; overflow-y: hidden; margin: 12px 0; padding-block: 4px; }
math { font-family: 'STIX Two Math', math; font-size: 1.08em; }
math[display="block"] { margin: 0; }
.katex-error, mstyle[mathcolor] { color: var(--red); }
.exo-intro { margin-bottom: var(--cell); }
.parts { list-style: none; margin: 0; padding: 0; display: grid; gap: calc(var(--cell) * 1.25); }
.part { position: relative; }
/* The question number sits in the margin, as on a handwritten copie. */
.part-num { position: absolute; inset-inline-end: calc(100% + 10px); top: 0; font: 700 1rem/1.65 var(--sans); color: var(--ink); }
@media (max-width: 480px) { .part-num { inset-inline-end: calc(100% + 18px); font-size: .9375rem; } }
.part-body { min-width: 0; }
details.hint, details.answer { margin-top: 10px; font-family: var(--sans); }
details summary { cursor: pointer; min-height: 44px; display: inline-flex; align-items: center; font-weight: 700; }
details.hint summary { color: var(--red); }
details.answer summary { color: var(--pen); }
details .rich { font-family: var(--serif); padding: 4px 0 4px 12px; border-inline-start: 2px solid currentColor; }
details.hint .rich { border-color: var(--red); }
details.answer .rich { border-color: var(--pen); }
.locked .teaser, .answer-locked { font: italic .9375rem/1.5 var(--sans); color: var(--muted); }
.locked .teaser { padding: 10px 12px; border: 1px dashed var(--line); background: var(--sheet); }
.unlock { margin-top: calc(var(--cell) * 1.5); padding-top: var(--cell); border-top: 1px solid var(--line); }
.unlock p { font-family: var(--sans); line-height: 1.5; }

/* ---------------------------------------------------------------- lists of exercises */
.exo-list, .admin-list { list-style: none; margin: 0 0 24px; padding: 0; border-top: 1px solid var(--line); }
.exo-list li, .admin-list li { border-bottom: 1px solid var(--line); }
.exo-list a, .admin-list a { display: grid; gap: 2px; padding-block: 12px; min-height: 52px; text-decoration: none; color: var(--ink); }
.exo-list a:hover .row-title, .admin-list a:hover .row-title { text-decoration: underline; }
.row-title { font: 600 1.0625rem/1.35 var(--serif); }
.row-meta { display: flex; flex-wrap: wrap; gap: 4px 12px; font-family: var(--sans); }
.lock-tag { color: var(--red); }
.crumbs { font: .9375rem var(--sans); margin-bottom: 4px; }
.level-list li > span:first-child { flex: 1; }
.level-list a { justify-content: space-between; gap: 12px; }
.empty { padding: 20px; border: 1px dashed var(--line); color: var(--muted); font-family: var(--sans); }

/* ---------------------------------------------------------------- admin */
.admin-nav, .filters { display: flex; gap: 4px; overflow-x: auto; border-bottom: 1px solid var(--line); margin-bottom: 20px; font-family: var(--sans); scrollbar-width: none; }
.admin-nav a, .filters a { padding: 10px 12px; min-height: 44px; display: inline-flex; align-items: center; white-space: nowrap; text-decoration: none; color: var(--muted); border-bottom: 3px solid transparent; }
.admin-nav a[aria-current], .filters a[aria-current] { color: var(--ink); border-bottom-color: var(--pen); font-weight: 700; }
.filters { border-bottom: 0; margin-bottom: 8px; }
.head { display: flex; justify-content: space-between; align-items: center; gap: 12px; flex-wrap: wrap; margin-bottom: 12px; }
.head h1 { margin: 0; }
.actions { display: flex; flex-wrap: wrap; gap: 10px; }
.state { font-weight: 700; }
.state.draft { color: var(--muted); }
.state.scheduled { color: var(--warn); }
.state.published { color: var(--ok); }
.card { background: var(--sheet); border: 1px solid var(--line); border-radius: 6px; padding: 16px; margin: 0 0 16px; display: grid; gap: 14px; min-width: 0; }
fieldset.card legend { font: 700 1rem var(--sans); padding: 0 6px; }
.part-edit.new { border-style: dashed; }
.field { display: grid; gap: 6px; min-width: 0; border: 0; padding: 0; margin: 0; }
.field legend { font: 700 .9375rem var(--sans); padding: 0; margin-bottom: 6px; }
.grid2 { display: grid; grid-template-columns: repeat(auto-fit, minmax(14rem, 1fr)); gap: 14px; }
.radios { display: flex; flex-wrap: wrap; gap: 0 18px; }
input[type=radio] { width: 20px; height: 20px; accent-color: var(--pen); }
/* :where() keeps this at zero specificity so component rules (.chap-row, .pos…) can size inputs. */
:where(input:not([type=checkbox]):not([type=radio]):not([type=file]), select, textarea) {
  width: 100%; min-height: 46px; padding: 10px 12px; border: 1px solid var(--line); border-radius: 6px; background: var(--paper); color: var(--ink); }
textarea { font: 400 1rem/1.5 ui-monospace, Menlo, monospace; resize: vertical; }
.hint { font: .875rem var(--sans); color: var(--muted); margin: 0; }
.narrow-field { max-width: 16rem; }
.preview { padding: 12px; border: 1px solid var(--line); border-inline-start: 3px solid var(--pen); background: var(--paper); font-family: var(--serif); }
.mathbar { position: sticky; top: 0; z-index: 1; display: flex; gap: 6px; overflow-x: auto; padding: 8px 0; margin-bottom: 8px; background: var(--paper); border-bottom: 1px solid var(--line); scrollbar-width: thin; }
.chip { flex: none; min-width: 44px; min-height: 44px; padding: 0 10px; border: 1px solid var(--line); border-radius: 6px; background: var(--sheet); color: var(--ink); font: 400 1rem var(--serif); cursor: pointer; }
.chip:hover { border-color: var(--pen); }
.sticky-actions { position: sticky; bottom: 0; padding: 12px 0; background: var(--paper); border-top: 1px solid var(--line); }
.btn.small { min-height: 44px; padding: 0 14px; font-size: .9375rem; }
.link { background: none; border: 0; padding: 0; min-height: 44px; font: inherit; color: var(--pen); text-decoration: underline; cursor: pointer; }
.link.danger { color: var(--red); }
.chap-level { margin-bottom: 28px; }
.chap-list { list-style: none; margin: 0 0 12px; padding: 0; border-top: 1px solid var(--line); }
.chap-list li { display: flex; flex-wrap: wrap; gap: 4px 12px; align-items: center; padding-block: 8px; border-bottom: 1px solid var(--line); }
.chap-row { display: flex; gap: 8px; align-items: center; flex: 1 1 16rem; min-width: 0; }
.chap-row input.pos { width: 4rem; flex: none; }
.chap-row input[name=name] { flex: 1; min-width: 0; }
.chap-row .btn { flex: none; }
.chap-add .row { display: flex; gap: 8px; }
.chap-add .row input { flex: 1; min-width: 0; }
.media-grid { list-style: none; padding: 0; display: grid; grid-template-columns: repeat(auto-fill, minmax(10rem, 1fr)); gap: 12px; }
.media-grid li { display: grid; gap: 6px; }
.media-grid img { width: 100%; aspect-ratio: 4 / 3; object-fit: contain; background: #fff; border: 1px solid var(--line); }
.snippet { overflow-wrap: anywhere; }
.preview-bar { display: flex; flex-wrap: wrap; gap: 8px 16px; padding: 10px 12px; background: var(--sheet); border: 1px solid var(--line); font-family: var(--sans); }
.flash ul { margin: 6px 0 0; padding-inline-start: 1.2em; }
.sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }

@media (prefers-reduced-motion: reduce) { * { transition: none !important; animation: none !important; } }