/* ---------- Theme tokens ---------- */
:root {
  --bg: #f6f7f9;
  --surface: #ffffff;
  --surface-2: #f0f2f5;
  --border: #dde1e7;
  --text: #1c2330;
  --text-2: #586274;
  --accent: #3b5bdb;
  --accent-soft: #e7ecfd;
  --good: #2b8a3e;
  --good-soft: #e3f6e8;
  --bad: #c92a2a;
  --bad-soft: #fde8e8;
  --warn: #b35c00;
  --easy: #2b8a3e;
  --medium: #b35c00;
  --hard: #c92a2a;
  --code-bg: #f4f5f8;
  --code-text: #1f2430;
  --tok-kw: #7c3aed;
  --tok-str: #0f7b3d;
  --tok-num: #b45309;
  --tok-com: #7a8494;
  --tok-fn: #1d4ed8;
  --shadow: 0 1px 2px rgba(16, 24, 40, .06), 0 1px 3px rgba(16, 24, 40, .08);
  --radius: 12px;
  --mono: ui-monospace, "SFMono-Regular", "JetBrains Mono", Menlo, Consolas, "Liberation Mono", monospace;
  --sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0f1218; --surface: #171b23; --surface-2: #1f2430; --border: #2c3341;
    --text: #e6e9ef; --text-2: #9aa3b2; --accent: #7c96ff; --accent-soft: #232c4a;
    --good: #51cf66; --good-soft: #15301d; --bad: #ff6b6b; --bad-soft: #3a1a1c; --warn: #ffa94d;
    --easy: #51cf66; --medium: #ffa94d; --hard: #ff6b6b;
    --code-bg: #12161d; --code-text: #dfe3ea;
    --tok-kw: #c4a5ff; --tok-str: #8ce99a; --tok-num: #ffc078; --tok-com: #7d8799; --tok-fn: #8ab4ff;
    --shadow: 0 1px 2px rgba(0, 0, 0, .4);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #0f1218; --surface: #171b23; --surface-2: #1f2430; --border: #2c3341;
  --text: #e6e9ef; --text-2: #9aa3b2; --accent: #7c96ff; --accent-soft: #232c4a;
  --good: #51cf66; --good-soft: #15301d; --bad: #ff6b6b; --bad-soft: #3a1a1c; --warn: #ffa94d;
  --easy: #51cf66; --medium: #ffa94d; --hard: #ff6b6b;
  --code-bg: #12161d; --code-text: #dfe3ea;
  --tok-kw: #c4a5ff; --tok-str: #8ce99a; --tok-num: #ffc078; --tok-com: #7d8799; --tok-fn: #8ab4ff;
  --shadow: 0 1px 2px rgba(0, 0, 0, .4);
  color-scheme: dark;
}

/* ---------- Base ---------- */
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0; background: var(--bg); color: var(--text);
  font: 16px/1.6 var(--sans);
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
h1, h2, h3 { line-height: 1.25; margin: 0 0 .5rem; }
h1 { font-size: 1.6rem; }
h2 { font-size: 1.2rem; }
h3 { font-size: 1.02rem; }
p { margin: 0 0 .75rem; }
code { font-family: var(--mono); font-size: .9em; background: var(--surface-2); padding: .08em .35em; border-radius: 5px; }
main { max-width: 980px; margin: 0 auto; padding: 8px 16px 64px; outline: none; }
.muted { color: var(--text-2); }
.small { font-size: .875rem; }
.hidden { display: none !important; }

/* ---------- Top bar ---------- */
.topbar {
  position: sticky; top: 0; z-index: 10;
  display: flex; align-items: center; gap: 12px;
  padding: 10px 16px; background: var(--surface); border-bottom: 1px solid var(--border);
}
.brand { display: flex; align-items: center; gap: 8px; color: var(--text); font-weight: 700; white-space: nowrap; }
.brand:hover { text-decoration: none; }
.brand-mark {
  display: inline-grid; place-items: center; width: 28px; height: 28px; border-radius: 8px;
  background: var(--accent); color: #fff; font-size: 15px;
}
.search { flex: 1; max-width: 460px; margin-left: auto; }
.search input {
  width: 100%; padding: 8px 12px; border-radius: 10px; border: 1px solid var(--border);
  background: var(--surface-2); color: var(--text); font: inherit; font-size: .95rem;
}
.search input:focus { outline: 2px solid var(--accent); outline-offset: 0; background: var(--surface); }
.icon-btn {
  width: 38px; height: 38px; border-radius: 10px; border: 1px solid var(--border);
  background: var(--surface); color: var(--text); font-size: 18px; cursor: pointer; flex: none;
}
.icon-btn:hover { background: var(--surface-2); }

/* ---------- Breadcrumb ---------- */
.breadcrumb {
  max-width: 980px; margin: 0 auto; padding: 14px 16px 4px;
  font-size: .9rem; color: var(--text-2); display: flex; flex-wrap: wrap; gap: 4px;
}
.breadcrumb .sep { opacity: .6; padding: 0 2px; }
.breadcrumb .current { color: var(--text); font-weight: 600; }

/* ---------- Layout pieces ---------- */
.page-head { display: flex; flex-wrap: wrap; align-items: flex-end; justify-content: space-between; gap: 12px; margin: 8px 0 18px; }
.page-head p { margin: 0; }
.grid { display: grid; gap: 14px; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); }
.grid-3 { display: grid; gap: 14px; grid-template-columns: repeat(3, 1fr); }
.section-title { margin: 28px 0 12px; font-size: .8rem; text-transform: uppercase; letter-spacing: .08em; color: var(--text-2); font-weight: 700; }

.card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px; box-shadow: var(--shadow);
}
a.card, button.card { display: block; color: inherit; text-align: left; font: inherit; cursor: pointer; width: 100%; }
a.card:hover, button.card:hover { border-color: var(--accent); text-decoration: none; }
.card h2, .card h3 { margin-bottom: 6px; }
.card .stats { display: flex; flex-wrap: wrap; gap: 4px 14px; font-size: .875rem; color: var(--text-2); }
.card .stats b { color: var(--text); font-weight: 600; }
.domain-card { padding: 18px; }
.domain-card .tag { display: inline-block; font-size: .75rem; font-weight: 700; letter-spacing: .06em; color: var(--accent); margin-bottom: 6px; text-transform: uppercase; }

.progress { height: 6px; background: var(--surface-2); border-radius: 99px; overflow: hidden; margin: 10px 0 2px; }
.progress > span { display: block; height: 100%; background: var(--accent); border-radius: 99px; }

.level-card { border-top: 4px solid var(--border); display: flex; flex-direction: column; }
.level-card.easy { border-top-color: var(--easy); }
.level-card.medium { border-top-color: var(--medium); }
.level-card.hard { border-top-color: var(--hard); }
.level-card .btn { margin-top: auto; }
.level-card .stats { margin-bottom: 12px; }

.diff { font-size: .72rem; font-weight: 700; text-transform: uppercase; letter-spacing: .05em; padding: 2px 8px; border-radius: 99px; background: var(--surface-2); }
.diff.easy { color: var(--easy); }
.diff.medium { color: var(--medium); }
.diff.hard { color: var(--hard); }

/* ---------- Buttons & controls ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  padding: 9px 16px; border-radius: 10px; border: 1px solid var(--border);
  background: var(--surface); color: var(--text); font: inherit; font-size: .95rem; font-weight: 600;
  cursor: pointer; text-decoration: none; white-space: nowrap;
}
.btn:hover { background: var(--surface-2); text-decoration: none; }
.btn:disabled { opacity: .45; cursor: not-allowed; }
.btn-primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn-primary:hover { background: var(--accent); filter: brightness(1.08); }
.btn-danger { color: var(--bad); }
.btn-row { display: flex; flex-wrap: wrap; gap: 8px; }

.options-bar {
  display: flex; flex-wrap: wrap; align-items: center; gap: 12px 24px;
  padding: 12px 16px; background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  margin-bottom: 18px;
}
.options-bar .label { font-size: .85rem; color: var(--text-2); font-weight: 600; margin-right: 8px; }
.seg { display: inline-flex; border: 1px solid var(--border); border-radius: 10px; overflow: hidden; }
.seg button { border: 0; background: var(--surface); color: var(--text); padding: 6px 12px; font: inherit; font-size: .9rem; cursor: pointer; }
.seg button + button { border-left: 1px solid var(--border); }
.seg button.on { background: var(--accent); color: #fff; }

.mode-card .count { font-size: 1.5rem; font-weight: 700; }

/* ---------- Quiz ---------- */
.quiz-top { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin: 4px 0 10px; flex-wrap: wrap; }
.quiz-meta { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; font-size: .85rem; color: var(--text-2); }
.timer { font-variant-numeric: tabular-nums; font-weight: 700; color: var(--text); }
.timer.low { color: var(--bad); }
.qprogress { height: 4px; background: var(--surface-2); border-radius: 99px; overflow: hidden; margin-bottom: 16px; }
.qprogress span { display: block; height: 100%; background: var(--accent); }

.question { font-size: 1.08rem; font-weight: 500; margin-bottom: 14px; white-space: pre-line; }
.star { background: none; border: 0; font-size: 1.5rem; line-height: 1; cursor: pointer; color: var(--text-2); padding: 4px; }
.star.on { color: #f0a500; }

pre.code {
  margin: 0 0 16px; padding: 14px 16px; background: var(--code-bg); color: var(--code-text);
  border: 1px solid var(--border); border-radius: 10px; overflow-x: auto;
  font: 14px/1.55 var(--mono); tab-size: 4; white-space: pre;
}
pre.code code { background: none; padding: 0; font-size: inherit; border-radius: 0; }
.tok-kw { color: var(--tok-kw); font-weight: 600; }
.tok-str { color: var(--tok-str); }
.tok-num { color: var(--tok-num); }
.tok-com { color: var(--tok-com); font-style: italic; }
.tok-fn { color: var(--tok-fn); }

.opts { display: grid; gap: 10px; margin-bottom: 16px; }
.opt {
  display: flex; gap: 12px; align-items: flex-start; width: 100%; text-align: left;
  padding: 12px 14px; border-radius: 10px; border: 1.5px solid var(--border);
  background: var(--surface); color: var(--text); font: inherit; cursor: pointer;
}
.opt:hover:not(:disabled) { border-color: var(--accent); }
.opt:disabled { cursor: default; }
.opt .key {
  flex: none; display: inline-grid; place-items: center; width: 26px; height: 26px; border-radius: 7px;
  background: var(--surface-2); font-weight: 700; font-size: .85rem;
}
.opt .txt { white-space: pre-wrap; word-break: break-word; padding-top: 1px; }
.opt.mono .txt { font-family: var(--mono); font-size: .92rem; }
.opt.correct { border-color: var(--good); background: var(--good-soft); }
.opt.correct .key { background: var(--good); color: #fff; }
.opt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.opt.wrong .key { background: var(--bad); color: #fff; }
.opt.selected { border-color: var(--accent); background: var(--accent-soft); }
.opt.selected .key { background: var(--accent); color: #fff; }

.explain { border-left: 4px solid var(--accent); }
.explain.good { border-left-color: var(--good); }
.explain.bad { border-left-color: var(--bad); }
.explain h3 { margin-bottom: 6px; }
.explain .verdict.good { color: var(--good); }
.explain .verdict.bad { color: var(--bad); }
.optexp { list-style: none; padding: 0; margin: 10px 0 0; display: grid; gap: 6px; }
.optexp li { display: flex; gap: 10px; font-size: .93rem; }
.optexp li .key { flex: none; font-weight: 700; width: 22px; }
.optexp li.is-correct .key { color: var(--good); }
.quiz-actions { display: flex; justify-content: space-between; gap: 8px; margin-top: 16px; flex-wrap: wrap; }
.kbd-hint { font-size: .8rem; color: var(--text-2); }
kbd { font-family: var(--mono); font-size: .78rem; border: 1px solid var(--border); border-bottom-width: 2px; border-radius: 5px; padding: 0 5px; background: var(--surface); }

.palette { display: flex; flex-wrap: wrap; gap: 6px; margin: 14px 0; }
.palette button {
  width: 34px; height: 34px; border-radius: 8px; border: 1px solid var(--border); background: var(--surface);
  color: var(--text); font: inherit; font-size: .85rem; cursor: pointer;
}
.palette button.answered { background: var(--accent-soft); border-color: var(--accent); }
.palette button.current { outline: 2px solid var(--accent); outline-offset: 1px; font-weight: 700; }

/* ---------- Summary ---------- */
.score-hero { display: flex; flex-wrap: wrap; gap: 14px; margin-bottom: 18px; }
.score-hero .card { flex: 1 1 160px; text-align: center; }
.score-hero .big { font-size: 2rem; font-weight: 800; line-height: 1.2; }
table.breakdown { width: 100%; border-collapse: collapse; font-size: .92rem; }
table.breakdown th, table.breakdown td { padding: 8px 10px; border-bottom: 1px solid var(--border); text-align: left; }
table.breakdown th { color: var(--text-2); font-weight: 600; font-size: .8rem; text-transform: uppercase; letter-spacing: .04em; }
table.breakdown td.num, table.breakdown th.num { text-align: right; font-variant-numeric: tabular-nums; }
.table-wrap { overflow-x: auto; }
.review-item { margin-bottom: 14px; }
.review-item .your { color: var(--bad); }
.review-item .right { color: var(--good); }
details.review-item summary { cursor: pointer; font-weight: 600; }

/* ---------- Search ---------- */
.result { margin-bottom: 10px; }
.result .meta { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; font-size: .8rem; color: var(--text-2); margin-bottom: 4px; }
mark { background: #ffe066; color: #1c2330; border-radius: 3px; padding: 0 2px; }

/* ---------- Dialog ---------- */
dialog {
  border: 1px solid var(--border); border-radius: 14px; padding: 0; max-width: min(420px, calc(100vw - 32px));
  background: var(--surface); color: var(--text); box-shadow: 0 10px 40px rgba(0, 0, 0, .3);
}
dialog::backdrop { background: rgba(10, 14, 20, .55); }
.dialog-body { padding: 20px; }
.dialog-actions { display: flex; justify-content: flex-end; gap: 8px; margin-top: 16px; }

.empty { text-align: center; padding: 40px 16px; color: var(--text-2); }
.footer-actions { margin-top: 36px; display: flex; flex-wrap: wrap; gap: 8px; justify-content: space-between; align-items: center; }

/* ---------- Responsive ---------- */
@media (max-width: 720px) {
  .grid-3 { grid-template-columns: 1fr; }
  h1 { font-size: 1.35rem; }
  .brand-text { display: none; }
  .question { font-size: 1rem; }
  pre.code { font-size: 13px; padding: 12px; }
  .score-hero .big { font-size: 1.6rem; }
}