/* Question Bank — EC & SE revision
   One stylesheet, custom properties, mobile-first, light + dark. */

*, *::before, *::after { box-sizing: border-box; }

:root {
  --bg: #f6f7f9;
  --surface: #ffffff;
  --surface-2: #eef0f4;
  --border: #d9dde5;
  --border-strong: #b9c0cc;
  --text: #171a1f;
  --text-dim: #5c6472;
  --accent: #2f5bd0;
  --accent-ink: #ffffff;
  --ec: #a54c08;
  --ec-soft: #fdf0e0;
  --se: #1d6f8b;
  --se-soft: #e2f1f6;
  --good: #17703c;
  --good-soft: #e4f4ea;
  --bad: #b3261e;
  --bad-soft: #fbe7e6;
  --shadow: 0 1px 2px rgba(16, 20, 28, .06), 0 6px 20px rgba(16, 20, 28, .06);
  --radius: 14px;
  --radius-sm: 9px;
  --maxw: 46rem;
  --font: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, "Cascadia Mono", Consolas, "Liberation Mono", monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1216;
    --surface: #171b21;
    --surface-2: #1f242c;
    --border: #2b323c;
    --border-strong: #3d4653;
    --text: #e8ecf2;
    --text-dim: #9aa4b2;
    --accent: #6f95ee;
    --accent-ink: #0f1216;
    --ec: #e9a23b;
    --ec-soft: #2c2214;
    --se: #5fbcd8;
    --se-soft: #12262e;
    --good: #62c98b;
    --good-soft: #14291d;
    --bad: #f08078;
    --bad-soft: #2c1614;
    --shadow: 0 1px 2px rgba(0, 0, 0, .4), 0 8px 24px rgba(0, 0, 0, .3);
  }
}

/* The toggle must beat the media query in both directions. */
:root[data-theme="light"] {
  --bg: #f6f7f9; --surface: #ffffff; --surface-2: #eef0f4;
  --border: #d9dde5; --border-strong: #b9c0cc;
  --text: #171a1f; --text-dim: #5c6472;
  --accent: #2f5bd0; --accent-ink: #ffffff;
  --ec: #a54c08; --ec-soft: #fdf0e0;
  --se: #1d6f8b; --se-soft: #e2f1f6;
  --good: #17703c; --good-soft: #e4f4ea;
  --bad: #b3261e; --bad-soft: #fbe7e6;
  --shadow: 0 1px 2px rgba(16, 20, 28, .06), 0 6px 20px rgba(16, 20, 28, .06);
  color-scheme: light;
}
:root[data-theme="dark"] {
  --bg: #0f1216; --surface: #171b21; --surface-2: #1f242c;
  --border: #2b323c; --border-strong: #3d4653;
  --text: #e8ecf2; --text-dim: #9aa4b2;
  --accent: #6f95ee; --accent-ink: #0f1216;
  --ec: #e9a23b; --ec-soft: #2c2214;
  --se: #5fbcd8; --se-soft: #12262e;
  --good: #62c98b; --good-soft: #14291d;
  --bad: #f08078; --bad-soft: #2c1614;
  --shadow: 0 1px 2px rgba(0, 0, 0, .4), 0 8px 24px rgba(0, 0, 0, .3);
  color-scheme: dark;
}

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.55 var(--font);
  min-height: 100svh;
  display: flex;
  flex-direction: column;
  overflow-wrap: break-word;
}

code {
  font: 0.875em/1.4 var(--mono);
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 5px;
  padding: .08em .34em;
}

.skip {
  position: absolute; left: -999px; top: 0; z-index: 20;
  background: var(--accent); color: var(--accent-ink);
  padding: .6rem 1rem; border-radius: 0 0 var(--radius-sm) 0;
}
.skip:focus { left: 0; }

.announcer {
  position: absolute; width: 1px; height: 1px; margin: -1px;
  padding: 0; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0;
}

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

.topbar {
  position: sticky; top: 0; z-index: 10;
  display: flex; align-items: center; justify-content: space-between; gap: 1rem;
  padding: .6rem max(.9rem, env(safe-area-inset-left)) .6rem max(.9rem, env(safe-area-inset-right));
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(160%) blur(10px);
  border-bottom: 1px solid var(--border);
}

.brand {
  display: inline-flex; align-items: center; gap: .55rem;
  min-height: 2.25rem; margin: -.5rem; padding: .5rem;  /* keeps the tap target ≥44px */
  color: inherit; text-decoration: none; font-weight: 650; letter-spacing: -.01em;
  border-radius: var(--radius-sm);
}
.brand-mark {
  width: 1.15rem; height: 1.15rem; border-radius: 6px;
  background: linear-gradient(140deg, var(--ec), var(--se));
}
.topbar-actions { display: flex; align-items: center; gap: .5rem; }

.session-score {
  font-variant-numeric: tabular-nums;
  font-size: .875rem; color: var(--text-dim);
  background: var(--surface); border: 1px solid var(--border);
  border-radius: 999px; padding: .2rem .65rem;
}

.icon-btn {
  display: grid; place-items: center;
  width: 2.75rem; height: 2.75rem;
  border: 1px solid var(--border); border-radius: 50%;
  background: var(--surface); color: var(--text-dim);
  font-size: 1rem; cursor: pointer;
}
.icon-btn:hover { color: var(--text); border-color: var(--border-strong); }

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

main {
  flex: 1;
  width: 100%; max-width: var(--maxw);
  margin: 0 auto;
  padding: 1.25rem max(.9rem, env(safe-area-inset-left)) 4rem max(.9rem, env(safe-area-inset-right));
}
main:focus { outline: none; }

.loading { color: var(--text-dim); text-align: center; padding: 3rem 0; }

h1 { font-size: 1.55rem; line-height: 1.25; letter-spacing: -.02em; margin: 0 0 .35rem; }
h2 { font-size: 1.05rem; letter-spacing: -.01em; margin: 2rem 0 .75rem; }
.lede { color: var(--text-dim); margin: 0 0 1.5rem; }

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

.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: .4rem;
  min-height: 2.75rem; padding: .55rem 1.1rem;
  font: inherit; font-weight: 560;
  border: 1px solid var(--border-strong); border-radius: var(--radius-sm);
  background: var(--surface); color: var(--text);
  cursor: pointer; text-decoration: none;
}
.btn:hover { background: var(--surface-2); }
.btn-primary {
  background: var(--accent); border-color: var(--accent); color: var(--accent-ink);
}
.btn-primary:hover { filter: brightness(1.08); background: var(--accent); }
.btn-danger { color: var(--bad); border-color: color-mix(in srgb, var(--bad) 45%, var(--border)); }
.btn-danger:hover { background: var(--bad-soft); }
.btn-quiet { border-color: transparent; background: transparent; color: var(--text-dim); }
.btn-quiet:hover { background: var(--surface-2); color: var(--text); }
.btn[disabled] { opacity: .45; cursor: not-allowed; }
.btn-row { display: flex; flex-wrap: wrap; gap: .6rem; }

:where(button, a, [tabindex]):focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

/* ---------- home: subjects ---------- */

.subjects { display: grid; gap: 2.25rem; }

/* Two subjects abreast once there is genuinely room for them. */
@media (min-width: 64rem) {
  main { max-width: 76rem; }
  .subjects { grid-template-columns: 1fr 1fr; gap: 2.75rem; }
}

/* Queried by the subject column's own width, not the window's — once the two
   subjects sit side by side the viewport says nothing about how much room a
   module grid actually has. Without container-query support the cards stay
   one-up, which is a fine fallback. */
.subject { container-type: inline-size; }

.subject-head {
  display: flex; align-items: baseline; justify-content: space-between; gap: 1rem;
  padding-bottom: .5rem; margin-bottom: .85rem;
  border-bottom: 2px solid var(--sub, var(--border));
}
.subject-head h2 { margin: 0; font-size: 1.15rem; color: var(--sub, var(--text)); }
.subject-head .meta { font-size: .8125rem; color: var(--text-dim); font-variant-numeric: tabular-nums; }

.subject[data-subject="ec"] { --sub: var(--ec); --sub-soft: var(--ec-soft); }
.subject[data-subject="se"] { --sub: var(--se); --sub-soft: var(--se-soft); }

.modules { display: grid; gap: .7rem; grid-template-columns: 1fr; }
@container (min-width: 30rem) { .modules { grid-template-columns: 1fr 1fr; } }

.module-card {
  display: flex; flex-direction: column; gap: .55rem;
  padding: .9rem 1rem;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); box-shadow: var(--shadow);
  text-align: left; font: inherit; color: inherit;
  cursor: pointer; width: 100%;
}
.module-card:hover { border-color: var(--sub); }
.module-card .m-num {
  font-size: .6875rem; font-weight: 700; letter-spacing: .09em; text-transform: uppercase;
  color: var(--sub);
}
.module-card .m-name { font-weight: 600; line-height: 1.3; }
.module-card .m-stats {
  display: flex; justify-content: space-between; gap: .75rem;
  font-size: .8125rem; color: var(--text-dim); font-variant-numeric: tabular-nums;
}

/* Whole-subject mixed pool — spans the grid under the four module cards. */
.all-card {
  grid-column: 1 / -1;
  background: linear-gradient(180deg, var(--sub-soft, var(--surface-2)), var(--surface) 70%);
  border-color: color-mix(in srgb, var(--sub, var(--border)) 40%, var(--border));
}
.all-card .m-name { color: var(--text-dim); font-weight: 500; font-size: .875rem; }

.bar {
  height: 5px; border-radius: 999px; background: var(--surface-2);
  overflow: hidden; border: 1px solid var(--border);
}
.bar > span { display: block; height: 100%; background: var(--sub, var(--accent)); }
.bar.done > span { background: var(--good); }

/* ---------- home footer ---------- */

.home-foot {
  margin-top: 2.5rem; padding-top: 1.25rem; border-top: 1px solid var(--border);
  color: var(--text-dim); font-size: .875rem;
}
.home-foot h2 { margin-top: 0; font-size: .9375rem; }
.reset-panel { display: grid; gap: .6rem; }
.reset-confirm {
  padding: .9rem 1rem; border-radius: var(--radius);
  background: var(--bad-soft); border: 1px solid color-mix(in srgb, var(--bad) 35%, transparent);
  color: var(--text);
}
.reset-confirm p { margin: 0 0 .75rem; }

/* ---------- start panel ---------- */

.start-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 1.1rem 1.15rem;
}
.start-card[data-subject="ec"] { --sub: var(--ec); --sub-soft: var(--ec-soft); }
.start-card[data-subject="se"] { --sub: var(--se); --sub-soft: var(--se-soft); }

.eyebrow {
  font-size: .6875rem; font-weight: 700; letter-spacing: .09em; text-transform: uppercase;
  color: var(--sub, var(--text-dim)); margin: 0 0 .25rem;
}

.stat-row {
  display: flex; flex-wrap: wrap; gap: .5rem 1.5rem;
  margin: 1rem 0; padding: .85rem 0; border-block: 1px solid var(--border);
  font-variant-numeric: tabular-nums;
}
.stat { display: grid; gap: .1rem; }
.stat b { font-size: 1.25rem; font-weight: 650; line-height: 1.1; }
.stat span { font-size: .75rem; color: var(--text-dim); }

fieldset { border: 0; padding: 0; margin: 0 0 1rem; }
legend { padding: 0; font-size: .8125rem; color: var(--text-dim); margin-bottom: .5rem; }

.sizes { display: flex; flex-wrap: wrap; gap: .5rem; }
.size {
  position: relative; min-height: 2.6rem; padding: .5rem 1rem;
  border: 1px solid var(--border-strong); border-radius: var(--radius-sm);
  background: var(--surface); color: var(--text); font: inherit; font-weight: 560;
  cursor: pointer; font-variant-numeric: tabular-nums;
}
.size[aria-pressed="true"] {
  background: var(--sub, var(--accent)); border-color: var(--sub, var(--accent));
  color: var(--surface);
}
.size[disabled] { opacity: .4; cursor: not-allowed; }

.note {
  font-size: .8125rem; color: var(--text-dim); margin: 0 0 1rem;
}
.note.warn {
  background: var(--surface-2); border: 1px solid var(--border);
  border-radius: var(--radius-sm); padding: .7rem .85rem; color: var(--text);
}

.topic-list { font-size: .8125rem; color: var(--text-dim); margin: 1.25rem 0 0; }
.topic-list summary { cursor: pointer; color: var(--text); }
.topic-list ul { margin: .6rem 0 0; padding-left: 1.1rem; display: grid; gap: .2rem; }

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

.quiz-head {
  display: flex; align-items: center; justify-content: space-between; gap: 1rem;
  margin-bottom: .35rem;
}
.quiz-head .crumb { font-size: .8125rem; color: var(--text-dim); }
.quiz-head .crumb b { color: var(--sub, var(--text)); font-weight: 650; }

.progress-track {
  height: 4px; border-radius: 999px; background: var(--surface-2);
  border: 1px solid var(--border); overflow: hidden; margin-bottom: 1.25rem;
}
.progress-track > span { display: block; height: 100%; background: var(--sub, var(--accent)); transition: width .18s ease; }

.quiz[data-subject="ec"] { --sub: var(--ec); --sub-soft: var(--ec-soft); }
.quiz[data-subject="se"] { --sub: var(--se); --sub-soft: var(--se-soft); }

.chip {
  display: inline-block; font-size: .6875rem; font-weight: 650;
  letter-spacing: .04em; text-transform: uppercase;
  color: var(--sub, var(--text-dim));
  background: var(--sub-soft, var(--surface-2));
  border-radius: 999px; padding: .22rem .6rem; margin-bottom: .7rem;
}

.stem {
  font-size: 1.1875rem; line-height: 1.45; font-weight: 500;
  letter-spacing: -.01em; margin: 0 0 1.1rem;
}

.options { display: grid; gap: .55rem; margin-bottom: 1.25rem; }

.option {
  display: grid; grid-template-columns: 1.85rem 1fr auto; align-items: start; gap: .7rem;
  width: 100%; min-height: 3rem; padding: .8rem .9rem;
  text-align: left; font: inherit; color: inherit;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); cursor: pointer;
}
.option:hover:not([disabled]) { border-color: var(--border-strong); background: var(--surface-2); }
.option[disabled] { cursor: default; }

.option .letter {
  display: grid; place-items: center;
  width: 1.85rem; height: 1.85rem; border-radius: 7px;
  background: var(--surface-2); border: 1px solid var(--border);
  font-size: .8125rem; font-weight: 700; color: var(--text-dim);
}
.option .mark { font-size: 1rem; line-height: 1.85rem; }

.option.correct {
  background: var(--good-soft);
  border-color: color-mix(in srgb, var(--good) 55%, transparent);
}
.option.correct .letter { background: var(--good); border-color: var(--good); color: var(--surface); }
.option.correct .mark { color: var(--good); }

.option.wrong {
  background: var(--bad-soft);
  border-color: color-mix(in srgb, var(--bad) 55%, transparent);
}
.option.wrong .letter { background: var(--bad); border-color: var(--bad); color: var(--surface); }
.option.wrong .mark { color: var(--bad); }

.option.muted { opacity: .55; }

.verdict {
  border-radius: var(--radius); padding: .95rem 1.05rem; margin-bottom: 1.25rem;
  background: var(--surface); border: 1px solid var(--border);
  border-left: 4px solid var(--border-strong);
}
.verdict.is-correct { border-left-color: var(--good); background: var(--good-soft); }
.verdict.is-wrong { border-left-color: var(--bad); background: var(--bad-soft); }
.verdict .verdict-head {
  font-weight: 650; margin: 0 0 .35rem;
  display: flex; align-items: center; gap: .5rem;
}
.verdict.is-correct .verdict-head { color: var(--good); }
.verdict.is-wrong .verdict-head { color: var(--bad); }
.verdict p:last-child { margin: 0; }

.quiz-foot {
  display: flex; align-items: center; justify-content: space-between; gap: 1rem;
  padding-top: 1rem; border-top: 1px solid var(--border);
}
.keyhint { font-size: .75rem; color: var(--text-dim); }
.keyhint kbd {
  font: .9em var(--mono); background: var(--surface-2);
  border: 1px solid var(--border); border-bottom-width: 2px;
  border-radius: 4px; padding: .05em .35em;
}
@media (max-width: 33rem) { .keyhint { display: none; } }

/* ---------- results ---------- */

.score-hero {
  text-align: center; padding: 1.75rem 1rem;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); box-shadow: var(--shadow); margin-bottom: 1.5rem;
}
.score-hero .pct {
  font-size: 3rem; font-weight: 700; letter-spacing: -.03em; line-height: 1;
  font-variant-numeric: tabular-nums; color: var(--sub, var(--accent));
}
.score-hero .frac { color: var(--text-dim); margin: .35rem 0 0; }
.score-hero[data-subject="ec"] { --sub: var(--ec); }
.score-hero[data-subject="se"] { --sub: var(--se); }

.review { display: grid; gap: .8rem; margin-bottom: 1.75rem; }
.review-item {
  background: var(--surface); border: 1px solid var(--border);
  border-left: 4px solid var(--bad);
  border-radius: var(--radius); padding: .9rem 1rem;
}
.review-item .r-stem { font-weight: 560; margin: .35rem 0 .6rem; }
.review-item .r-line { font-size: .875rem; margin: .2rem 0; }
.review-item .r-line .tag {
  display: inline-block; min-width: 4.6rem; color: var(--text-dim);
}
.review-item .r-yours { color: var(--bad); }
.review-item .r-right { color: var(--good); }
.review-item .r-why { font-size: .875rem; color: var(--text-dim); margin: .6rem 0 0; }

/* ---------- misc ---------- */

.empty {
  text-align: center; padding: 2.5rem 1rem; color: var(--text-dim);
  background: var(--surface); border: 1px dashed var(--border); border-radius: var(--radius);
}

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