:root {
  --bg: #f6f5fb;
  --surface: #ffffff;
  --surface-2: #f0eef8;
  --text: #1c1a29;
  --muted: #6b6880;
  --border: #e2dfee;
  --accent: #6a4fd6;
  --accent-ink: #ffffff;
  --accent-soft: #ece8fd;
  --ok: #1f7a4d;
  --ok-soft: #e3f4ea;
  --ok-border: #8fd0ab;
  --bad: #b3261e;
  --bad-soft: #fdeceb;
  --bad-border: #f0a8a3;
  --code-bg: #f7f6fb;
  --shadow: 0 1px 2px rgb(28 26 41 / 6%), 0 4px 16px rgb(28 26 41 / 5%);
  --radius: 14px;
  --mono: ui-monospace, "SF Mono", "Cascadia Code", "JetBrains Mono", Menlo, Consolas, monospace;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #121019;
    --surface: #1b1825;
    --surface-2: #231f30;
    --text: #ebe8f5;
    --muted: #9d98b3;
    --border: #2f2a3f;
    --accent: #9b85ff;
    --accent-ink: #120f1c;
    --accent-soft: #2a2442;
    --ok: #6fd69c;
    --ok-soft: #15291f;
    --ok-border: #2f6b48;
    --bad: #ff8a80;
    --bad-soft: #321a1a;
    --bad-border: #7a3430;
    --code-bg: #0d1117;
    --shadow: 0 1px 2px rgb(0 0 0 / 30%), 0 4px 16px rgb(0 0 0 / 25%);
    color-scheme: dark;
  }
}

* { box-sizing: border-box; }

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

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.55 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

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

.wrap { width: 100%; max-width: 760px; margin: 0 auto; padding: 0 16px; }
.wrap.narrow { max-width: 420px; }
.wrap.wide { max-width: 1000px; }
main.wrap { flex: 1; padding-bottom: 48px; }

.top { display: flex; align-items: center; padding-top: 20px; padding-bottom: 20px; }
.brand { display: inline-flex; align-items: center; gap: 10px; font-weight: 700; font-size: 18px; color: var(--text); text-decoration: none; letter-spacing: -0.01em; }

.foot { text-align: right; padding: 12px 16px; font-size: 12px; }
.foot a { color: var(--muted); text-decoration: none; }
.foot a:hover { color: var(--accent); text-decoration: underline; }

.muted { color: var(--muted); }
.small { font-size: 13px; }

.page-title { font-size: 28px; letter-spacing: -0.02em; margin: 8px 0 20px; }

.card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow); padding: 20px; }

code { font-family: var(--mono); font-size: 0.92em; background: var(--surface-2); padding: 0.1em 0.35em; border-radius: 5px; overflow-wrap: anywhere; }

pre.code { margin: 0; background: var(--code-bg); border: 1px solid var(--border); border-radius: 10px; padding: 14px 16px; overflow-x: auto; font-size: 14px; line-height: 1.5; }
pre.code code { background: none; padding: 0; font-size: inherit; overflow-wrap: normal; }
pre.code code.hljs { background: transparent; padding: 0; }

/* Buttons */
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; border: 1px solid var(--border); background: var(--surface); color: var(--text); font: inherit; font-weight: 600; padding: 11px 20px; border-radius: 10px; cursor: pointer; text-decoration: none; transition: background .15s, border-color .15s, transform .05s; }
.btn:hover { border-color: var(--accent); }
.btn:active { transform: translateY(1px); }
.btn:focus-visible, .choice:focus-visible, .chip:focus-visible, .track:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.btn.primary:hover { filter: brightness(1.08); }
.btn.ghost { background: transparent; }
.btn.small { padding: 6px 12px; font-size: 13px; border-radius: 8px; }
.btn:disabled { opacity: .5; cursor: not-allowed; }
.linkish { background: none; border: 0; color: var(--muted); font: inherit; font-size: 14px; cursor: pointer; padding: 4px; text-decoration: underline; }
.linkish:hover { color: var(--accent); }

/* Home */
.hero h1 { font-size: clamp(28px, 6vw, 40px); line-height: 1.15; letter-spacing: -0.03em; margin: 12px 0 8px; }
.hero p { color: var(--muted); margin: 0 0 28px; max-width: 34em; }
.step-label { font-size: 13px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.06em; color: var(--muted); margin: 28px 0 12px; }
.tracks { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 14px; }
.track { text-align: left; font: inherit; color: var(--text); background: var(--surface); border: 2px solid var(--border); border-radius: var(--radius); padding: 20px; cursor: pointer; box-shadow: var(--shadow); transition: border-color .15s, background .15s; }
.track:hover { border-color: var(--accent); }
.track[aria-pressed="true"] { border-color: var(--accent); background: var(--accent-soft); }
.track:disabled { opacity: .5; cursor: not-allowed; }
.track .name { font-size: 22px; font-weight: 700; letter-spacing: -0.02em; display: block; }
.track .count { color: var(--muted); font-size: 14px; }
.chips { display: flex; flex-wrap: wrap; gap: 10px; }
.chip { font: inherit; font-weight: 600; min-width: 56px; padding: 10px 16px; border-radius: 999px; border: 2px solid var(--border); background: var(--surface); color: var(--text); cursor: pointer; }
.chip:hover { border-color: var(--accent); }
.chip[aria-pressed="true"] { border-color: var(--accent); background: var(--accent); color: var(--accent-ink); }
.start-row { margin-top: 28px; }

/* Quiz */
.quiz-bar { display: flex; align-items: center; justify-content: space-between; gap: 12px; font-size: 14px; color: var(--muted); margin-bottom: 10px; flex-wrap: wrap; }
.quiz-bar strong { color: var(--text); }
.progress { height: 6px; background: var(--surface-2); border-radius: 99px; overflow: hidden; margin-bottom: 22px; }
.progress > span { display: block; height: 100%; background: var(--accent); border-radius: 99px; transition: width .3s; }
.tag { display: inline-block; font-size: 12px; font-weight: 600; padding: 3px 10px; border-radius: 99px; background: var(--accent-soft); color: var(--accent); }
.question .prompt { font-size: 19px; font-weight: 600; line-height: 1.45; margin: 12px 0 16px; letter-spacing: -0.01em; }
.question pre.code { margin-bottom: 20px; }
.choices { list-style: none; margin: 0; padding: 0; display: grid; gap: 10px; }
.choice { width: 100%; display: flex; align-items: flex-start; gap: 12px; text-align: left; font: inherit; color: var(--text); background: var(--surface); border: 2px solid var(--border); border-radius: 12px; padding: 12px 14px; cursor: pointer; transition: border-color .15s, background .15s; min-height: 52px; }
.choice:hover:not(:disabled) { border-color: var(--accent); }
.choice:disabled { cursor: default; }
.choice .key { flex: none; width: 28px; height: 28px; border-radius: 8px; display: grid; place-items: center; font-size: 13px; font-weight: 700; background: var(--surface-2); color: var(--muted); }
.choice .body { flex: 1; min-width: 0; padding-top: 2px; overflow-wrap: anywhere; }
.choice .body pre.code { margin: 2px 0 0; padding: 8px 10px; font-size: 13px; }
.choice.right { border-color: var(--ok-border); background: var(--ok-soft); }
.choice.right .key { background: var(--ok); color: var(--surface); }
.choice.wrong { border-color: var(--bad-border); background: var(--bad-soft); }
.choice.wrong .key { background: var(--bad); color: var(--surface); }
.choice.dim { opacity: .55; }
.feedback { margin-top: 18px; border-radius: 12px; padding: 16px 18px; border: 1px solid var(--border); background: var(--surface); }
.feedback.ok { border-color: var(--ok-border); background: var(--ok-soft); }
.feedback.bad { border-color: var(--bad-border); background: var(--bad-soft); }
.feedback .verdict { font-weight: 700; margin: 0 0 6px; }
.feedback.ok .verdict { color: var(--ok); }
.feedback.bad .verdict { color: var(--bad); }
.feedback p { margin: 0 0 8px; }
.feedback .src { font-size: 13px; margin: 0; }
.next-row { display: flex; justify-content: flex-end; align-items: center; gap: 12px; margin-top: 18px; }
.hint { font-size: 12px; color: var(--muted); }
.error-box { color: var(--bad); margin-top: 12px; }

/* Summary */
.score { text-align: center; padding: 28px 20px; }
.score .big { font-size: 56px; font-weight: 800; letter-spacing: -0.04em; line-height: 1; }
.score .pct { color: var(--muted); margin-top: 6px; }
.missed { display: grid; gap: 14px; margin-top: 14px; }
.missed .card p { margin: 0 0 10px; }
.missed .card pre.code { margin-bottom: 12px; }
.missed .answer { border-left: 3px solid var(--ok); padding-left: 12px; margin: 0 0 10px; }
.row { display: flex; gap: 10px; flex-wrap: wrap; justify-content: center; margin-top: 20px; }

/* Login & admin */
.login { display: grid; gap: 12px; }
.login label { font-weight: 600; font-size: 14px; }
input[type=password], input[type=search], select { font: inherit; color: var(--text); background: var(--surface); border: 1px solid var(--border); border-radius: 10px; padding: 10px 12px; min-width: 0; }
input:focus, select:focus { outline: 2px solid var(--accent); outline-offset: 1px; }
.flash { padding: 10px 14px; border-radius: 10px; }
.flash.bad { background: var(--bad-soft); color: var(--bad); border: 1px solid var(--bad-border); }
.admin-head { display: flex; justify-content: space-between; align-items: center; gap: 12px; }
.stats { display: grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap: 12px; margin-bottom: 16px; }
.stat { padding: 16px 18px; }
.stat-value { font-size: 30px; font-weight: 800; letter-spacing: -0.03em; }
.topics { display: grid; gap: 12px; margin-bottom: 16px; }
.topics summary { cursor: pointer; }
.topic-list { columns: 3 220px; margin: 12px 0 0; padding: 0; list-style: none; font-size: 14px; }
.topic-list li { break-inside: avoid; padding: 2px 0; }
.filters { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; padding: 14px; margin-bottom: 8px; }
.filters input[type=search] { flex: 1 1 220px; }
.qa { margin-bottom: 14px; }
.qa.disabled { opacity: .6; border-style: dashed; }
.qa-head { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; margin-bottom: 4px; }
.qa-head form { margin-left: auto; }
.qa .slug { font-size: 12px; }
.qa .prompt { font-weight: 600; margin: 10px 0 12px; }
.qa pre.code { margin-bottom: 12px; }
.answers { list-style: none; padding: 0; margin: 0 0 12px; display: grid; gap: 6px; }
.answers li { display: flex; gap: 10px; align-items: flex-start; padding: 6px 10px; border-radius: 8px; overflow-wrap: anywhere; }
.answers li > div { min-width: 0; flex: 1; }
.answers li.ok { background: var(--ok-soft); }
.answers li .mark { font-weight: 800; width: 1em; flex: none; }
.answers li.ok .mark { color: var(--ok); }
.answers li.no .mark { color: var(--bad); }
.answers pre.code { padding: 6px 10px; font-size: 13px; }
.explain { margin: 0 0 8px; }
.pager { display: flex; gap: 6px; flex-wrap: wrap; margin: 20px 0; }

@media (max-width: 520px) {
  .tracks { grid-template-columns: 1fr; }
  .question .prompt { font-size: 17px; }
  pre.code { font-size: 13px; padding: 12px; }
  .card { padding: 16px; }
}