/* ---------- Tokens ---------- */
:root {
  --bg: #fafaf7;
  --surface: #ffffff;
  --surface-2: #f3f3ef;
  --text: #1c1c1e;
  --text-muted: #5b5b62;
  --border: #e3e3dd;
  --accent: #2f6df6;
  --accent-contrast: #ffffff;
  --correct: #1f7a3d;
  --correct-bg: #e3f5e9;
  --wrong: #b3261e;
  --wrong-bg: #fbe6e4;
  --radius: 10px;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.04), 0 4px 12px rgba(0, 0, 0, 0.04);
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu,
    Cantarell, "Helvetica Neue", Arial, "Noto Sans", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas,
    "Liberation Mono", monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #14151a;
    --surface: #1d1f25;
    --surface-2: #262932;
    --text: #ececf1;
    --text-muted: #a0a3ad;
    --border: #2f323b;
    --accent: #6c9bff;
    --accent-contrast: #0c1020;
    --correct: #6ddc94;
    --correct-bg: #1f3a2a;
    --wrong: #ff8a82;
    --wrong-bg: #3a201e;
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.3), 0 4px 12px rgba(0, 0, 0, 0.35);
  }
}

/* ---------- Base ---------- */
* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  font-size: 17px;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

code { font-family: var(--font-mono); font-size: 0.95em; }

.container {
  max-width: 760px;
  margin: 0 auto;
  padding: 32px 20px 64px;
}

.page-header { margin-bottom: 28px; }
.page-header h1 { font-size: 1.9rem; margin: 0 0 6px; letter-spacing: -0.01em; }
.lede { color: var(--text-muted); margin: 0; }
.muted { color: var(--text-muted); }
.small { font-size: 0.875rem; }

.page-footer { margin-top: 48px; }

.back-link {
  display: inline-block;
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.9rem;
  margin-bottom: 12px;
}
.back-link:hover { color: var(--accent); }

.quiz-header h1 { font-size: 1.4rem; margin: 0 0 4px; }

/* ---------- Topic picker ---------- */
.topics {
  display: grid;
  gap: 14px;
  grid-template-columns: 1fr;
}
@media (min-width: 560px) {
  .topics { grid-template-columns: repeat(2, 1fr); }
}

.topic-card {
  display: block;
  text-decoration: none;
  color: inherit;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 18px 16px;
  box-shadow: var(--shadow);
  transition: transform 0.08s ease, border-color 0.15s ease;
}
.topic-card:hover, .topic-card:focus-visible {
  border-color: var(--accent);
  transform: translateY(-1px);
  outline: none;
}
.topic-card h2 { margin: 0 0 4px; font-size: 1.1rem; }
.topic-card p { margin: 0; color: var(--text-muted); font-size: 0.95rem; }

/* Personal-progress badge appended to a topic card once stats load. */
.topic-card .topic-stat {
  margin-top: 8px;
  font-size: 0.8rem;
  color: var(--accent);
  font-variant-numeric: tabular-nums;
}
.summary-card .personal-best {
  margin: 0 0 14px;
  color: var(--accent);
  font-weight: 600;
}

/* Non-clickable "Coming soon" subject cards. */
.topic-card.is-disabled {
  cursor: default;
  opacity: 0.6;
}
.topic-card.is-disabled:hover,
.topic-card.is-disabled:focus-visible {
  border-color: var(--border);
  transform: none;
}
.badge {
  display: inline-block;
  margin-left: 8px;
  padding: 2px 8px;
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  vertical-align: middle;
  border-radius: 999px;
  background: var(--surface-2);
  color: var(--text-muted);
  border: 1px solid var(--border);
}
.badge.badge-accent {
  background: var(--accent);
  color: var(--accent-contrast);
  border-color: var(--accent);
}

/* Recommended ("Mixed") difficulty card — accent emphasis. */
.topic-card.is-recommended {
  border-color: var(--accent);
  box-shadow: var(--shadow), 0 0 0 1px var(--accent) inset;
}

/* ---------- Quiz card ---------- */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow);
}

.card-head {
  display: flex;
  justify-content: flex-end;
  align-items: center;
  min-height: 1.1rem;
  margin-bottom: 6px;
}
.quiz-timer {
  font-family: var(--font-mono);
  font-size: 0.9rem;
  color: var(--text-muted);
  font-variant-numeric: tabular-nums;
}

.prompt {
  font-size: 1.2rem;
  margin: 0 0 18px;
  line-height: 1.4;
}

/* Multi-line prompts (e.g. code traces). Preserves newlines + indentation,
   wraps long lines on mobile rather than scrolling. */
.prompt-code {
  margin: 0 0 18px;
  padding: 14px 16px;
  font-family: var(--font-mono);
  font-size: 0.9em;
  line-height: 1.5;
  white-space: pre-wrap;
  overflow-wrap: anywhere;
  background: var(--surface-2);
  color: var(--text);
  border-radius: var(--radius);
}

.options {
  display: grid;
  gap: 10px;
}

.option {
  text-align: left;
  background: var(--surface-2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 12px 14px;
  font: inherit;
  cursor: pointer;
  transition: background 0.12s ease, border-color 0.12s ease;
}
.option:hover:not(:disabled) { border-color: var(--accent); }
.option:disabled { cursor: default; }
.option.correct {
  background: var(--correct-bg);
  border-color: var(--correct);
  color: var(--correct);
}
.option.wrong {
  background: var(--wrong-bg);
  border-color: var(--wrong);
  color: var(--wrong);
}

.numeric-input-row {
  display: flex;
  gap: 8px;
  align-items: stretch;
}
.numeric-input {
  flex: 1;
  font: inherit;
  padding: 12px 14px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--surface-2);
  color: var(--text);
}
.numeric-input:focus { outline: 2px solid var(--accent); outline-offset: 1px; }

.btn {
  font: inherit;
  background: var(--accent);
  color: var(--accent-contrast);
  border: none;
  border-radius: var(--radius);
  padding: 12px 18px;
  cursor: pointer;
  font-weight: 600;
}
.btn:hover { filter: brightness(1.05); }
.btn.secondary {
  background: var(--surface-2);
  color: var(--text);
  border: 1px solid var(--border);
  font-weight: 500;
}

.feedback {
  margin-top: 18px;
  padding: 14px 16px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--surface-2);
}
.feedback.correct { border-color: var(--correct); background: var(--correct-bg); color: var(--correct); }
.feedback.wrong { border-color: var(--wrong); background: var(--wrong-bg); color: var(--wrong); }
.feedback p { margin: 0; }

.row {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin-top: 14px;
}

.explanation {
  margin-top: 14px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 16px;
}
.explanation h3 { margin: 0 0 8px; font-size: 1rem; }
.explanation ol { margin: 0; padding-left: 22px; }
.explanation li { margin-bottom: 6px; }
.explanation li:last-child { margin-bottom: 0; }
.explanation .summary { margin: 0 0 10px; color: var(--text-muted); font-size: 0.95rem; }

/* ---------- Summary ---------- */
.summary-card { text-align: center; }
.summary-score {
  font-size: 2.4rem;
  font-weight: 700;
  margin: 6px 0 4px;
}
.summary-sub { color: var(--text-muted); margin: 0 0 22px; }

.review { text-align: left; margin-top: 22px; }
.review h2 { font-size: 1.1rem; margin: 0 0 12px; }
.review details {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 12px 14px;
  margin-bottom: 10px;
}
.review summary {
  cursor: pointer;
  font-weight: 500;
  list-style: none;
}
.review summary::-webkit-details-marker { display: none; }
.review summary::before { content: "+ "; color: var(--text-muted); }
.review details[open] summary::before { content: "- "; }
.review .answer-line {
  margin-top: 8px;
  color: var(--text-muted);
  font-size: 0.95rem;
}

.center-row { justify-content: center; }

/* ---------- Auth ---------- */
.auth-strip {
  display: flex;
  justify-content: flex-end;
  align-items: center;
  gap: 4px;
  font-size: 0.85rem;
  margin-bottom: 12px;
  min-height: 1.1rem;
  color: var(--text-muted);
}
.auth-strip .auth-email { color: var(--text-muted); }
.auth-link,
.auth-linklike {
  color: var(--accent);
  text-decoration: none;
  background: none;
  border: none;
  padding: 0;
  font: inherit;
  cursor: pointer;
}
.auth-link:hover,
.auth-linklike:hover { text-decoration: underline; }

.auth-forms {
  display: grid;
  gap: 18px;
  grid-template-columns: 1fr;
}
@media (min-width: 640px) {
  .auth-forms { grid-template-columns: 1fr 1fr; }
}
.auth-card { display: flex; flex-direction: column; }
.auth-card h2 { margin: 0 0 12px; font-size: 1.1rem; }
.auth-label {
  display: block;
  margin: 10px 0 4px;
  font-size: 0.9rem;
  color: var(--text-muted);
}
.auth-card .btn { margin-top: 16px; align-self: flex-start; }
.auth-error {
  margin: 0 0 8px;
  padding: 8px 12px;
  border-radius: var(--radius);
  background: var(--wrong-bg);
  border: 1px solid var(--wrong);
  color: var(--wrong);
  font-size: 0.9rem;
}

/* ---------- Timing breakdown ---------- */
.timing { text-align: left; margin-top: 26px; }
.timing h2 { font-size: 1.1rem; margin: 0 0 12px; }

.timing-stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(130px, 1fr));
  gap: 10px;
  margin-bottom: 18px;
}
.timing-stats .stat {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 12px 14px;
  display: flex;
  flex-direction: column;
  gap: 2px;
}
.stat-value {
  font-size: 1.25rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}
.stat-label { font-size: 0.8rem; color: var(--text-muted); }

.timing-list { list-style: none; margin: 0; padding: 0; }
.timing-item {
  display: flex;
  align-items: baseline;
  gap: 10px;
  padding: 10px 12px;
  margin-bottom: 8px;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
}
.timing-mark { flex: 0 0 auto; font-weight: 700; }
.timing-mark.correct { color: var(--correct); }
.timing-mark.wrong { color: var(--wrong); }
.timing-prompt {
  flex: 1 1 auto;
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.timing-time {
  flex: 0 0 auto;
  font-family: var(--font-mono);
  font-size: 0.9rem;
  color: var(--text-muted);
  font-variant-numeric: tabular-nums;
}

@media (max-width: 360px) {
  .timing-stats { grid-template-columns: 1fr; }
}