/* ============================================================
   StudyLab viewer — generic styles. No creator-specific values.
   The accent color is injected at runtime via --accent.
   ============================================================ */

:root {
  --accent: #4f46e5;          /* overridden by data.json creator.accent */
  --accent-weak: #4f46e51a;   /* set in JS from accent */
  --accent-soft: #4f46e510;

  --bg: #f6f7f9;
  --surface: #ffffff;
  --ink: #1a1d23;
  --ink-soft: #565c66;
  --ink-faint: #8a909a;
  --line: #e7e9ee;
  --ok: #16a34a;
  --ok-soft: #16a34a14;
  --bad: #dc2626;
  --bad-soft: #dc262614;

  --radius: 18px;
  --radius-sm: 12px;
  --shadow-sm: 0 1px 2px rgba(16, 20, 30, 0.04), 0 1px 3px rgba(16, 20, 30, 0.06);
  --shadow-md: 0 4px 12px rgba(16, 20, 30, 0.06), 0 10px 30px rgba(16, 20, 30, 0.07);
  --shadow-lg: 0 8px 24px rgba(16, 20, 30, 0.08), 0 24px 48px rgba(16, 20, 30, 0.10);

  --ease: cubic-bezier(0.22, 0.61, 0.36, 1);
}

* { box-sizing: border-box; }

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

body {
  margin: 0;
  font-family: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

.wrap {
  width: 100%;
  max-width: 720px;
  margin: 0 auto;
  padding: 0 20px;
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--surface);
  padding: 10px 16px;
  border-radius: 0 0 8px 0;
  z-index: 100;
}
.skip-link:focus { left: 0; }

/* ---------- Header ---------- */
.site-header {
  background: var(--surface);
  border-bottom: 1px solid var(--line);
  position: sticky;
  top: 0;
  z-index: 20;
  backdrop-filter: saturate(140%) blur(6px);
}
.header-inner {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding-top: 14px;
  padding-bottom: 14px;
}
.brand {
  display: flex;
  align-items: center;
  gap: 10px;
}
.brand__logo {
  height: 26px;
  width: auto;
}
.brand__wordmark {
  font-weight: 700;
  font-size: 1.15rem;
  letter-spacing: -0.02em;
  color: var(--ink);
}
.brand__tag {
  font-size: 0.7rem;
  color: var(--ink-faint);
  background: var(--accent-soft);
  border: 1px solid var(--accent-weak);
  color: var(--accent);
  padding: 3px 8px;
  border-radius: 999px;
  font-weight: 500;
  white-space: nowrap;
}
.personal-line {
  margin: 0;
  font-size: 0.9rem;
  color: var(--ink-soft);
}

/* ---------- Intro ---------- */
.intro { padding: 28px 0 8px; }
.intro__title {
  margin: 0 0 6px;
  font-size: 1.6rem;
  line-height: 1.2;
  letter-spacing: -0.02em;
  font-weight: 700;
}
.intro__subtitle {
  margin: 0;
  color: var(--ink-soft);
  font-size: 1rem;
}

/* ---------- Tabs ---------- */
.tabs {
  display: flex;
  gap: 6px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 5px;
  margin: 20px 0 22px;
  box-shadow: var(--shadow-sm);
}
.tab {
  flex: 1;
  appearance: none;
  border: 0;
  background: transparent;
  color: var(--ink-soft);
  font: inherit;
  font-weight: 600;
  font-size: 0.95rem;
  padding: 10px 14px;
  border-radius: 999px;
  cursor: pointer;
  transition: background 0.2s var(--ease), color 0.2s var(--ease);
}
.tab:hover { color: var(--ink); }
.tab.is-active {
  background: var(--accent);
  color: #fff;
  box-shadow: var(--shadow-sm);
}

/* ---------- Panels ---------- */
.panel { animation: fade-up 0.35s var(--ease); }
.panel.is-hidden { display: none; }
.is-hidden { display: none !important; }

@keyframes fade-up {
  from { opacity: 0; transform: translateY(6px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* ---------- Buttons ---------- */
.btn {
  appearance: none;
  font: inherit;
  font-weight: 600;
  border-radius: 999px;
  padding: 11px 20px;
  cursor: pointer;
  border: 1px solid transparent;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  transition: transform 0.12s var(--ease), background 0.2s var(--ease),
              box-shadow 0.2s var(--ease), border-color 0.2s var(--ease), opacity 0.2s;
}
.btn:active { transform: translateY(1px) scale(0.99); }
.btn:disabled { opacity: 0.45; cursor: not-allowed; }
.btn__icon { width: 16px; height: 16px; fill: none; stroke: currentColor; stroke-width: 2; stroke-linecap: round; stroke-linejoin: round; }

.btn--primary {
  background: var(--accent);
  color: #fff;
  box-shadow: var(--shadow-sm);
}
.btn--primary:not(:disabled):hover { box-shadow: var(--shadow-md); }

.btn--ghost {
  background: var(--surface);
  color: var(--ink-soft);
  border-color: var(--line);
}
.btn--ghost:hover { color: var(--ink); border-color: #d6dae1; }

/* ---------- Chip ---------- */
.chip {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  color: var(--accent);
  background: var(--accent-soft);
  border: 1px solid var(--accent-weak);
  padding: 4px 10px;
  border-radius: 999px;
  text-transform: uppercase;
}
.chip:empty { display: none; }

/* ============ Flashcards ============ */
.fc__meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 14px;
  min-height: 26px;
}
.fc__progress {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--ink-faint);
  font-variant-numeric: tabular-nums;
}

.fc__stage {
  display: flex;
  align-items: center;
  gap: 8px;
}

.fc__nav {
  flex: 0 0 auto;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--ink-soft);
  cursor: pointer;
  display: grid;
  place-items: center;
  box-shadow: var(--shadow-sm);
  transition: transform 0.12s var(--ease), color 0.2s, border-color 0.2s;
}
.fc__nav svg { width: 20px; height: 20px; fill: none; stroke: currentColor; stroke-width: 2.2; stroke-linecap: round; stroke-linejoin: round; }
.fc__nav:hover { color: var(--accent); border-color: var(--accent-weak); }
.fc__nav:active { transform: scale(0.94); }
.fc__nav:disabled { opacity: 0.35; cursor: not-allowed; }

/* The flip card */
.card {
  flex: 1 1 auto;
  perspective: 1600px;
  min-width: 0;
  height: 340px;
  cursor: pointer;
  outline: none;
}
.card:focus-visible .card__inner { box-shadow: var(--shadow-lg), 0 0 0 3px var(--accent-weak); }

.card__inner {
  position: relative;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  transition: transform 0.6s var(--ease);
  border-radius: var(--radius);
}
.card.is-flipped .card__inner { transform: rotateY(180deg); }

.card__face {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  border-radius: var(--radius);
  background: var(--surface);
  border: 1px solid var(--line);
  box-shadow: var(--shadow-md);
  padding: 28px 26px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  gap: 14px;
}
.card__back {
  transform: rotateY(180deg);
  background: linear-gradient(180deg, var(--accent-soft), var(--surface) 60%);
  border-color: var(--accent-weak);
}
.card__hint {
  position: absolute;
  top: 18px;
  left: 0;
  right: 0;
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  color: var(--ink-faint);
}
.card__back .card__hint { color: var(--accent); }
.card__text {
  margin: 0;
  font-size: 1.25rem;
  font-weight: 600;
  line-height: 1.4;
  letter-spacing: -0.01em;
}
.card__flip-hint {
  position: absolute;
  bottom: 16px;
  left: 0; right: 0;
  font-size: 0.72rem;
  color: var(--ink-faint);
}

.fc__controls {
  display: flex;
  gap: 10px;
  justify-content: center;
  margin-top: 20px;
}

/* ============ Quiz ============ */
.quiz__meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 18px;
}
.quiz__progress { font-size: 0.85rem; font-weight: 600; color: var(--ink-faint); font-variant-numeric: tabular-nums; }
.quiz__score {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--accent);
  background: var(--accent-soft);
  border: 1px solid var(--accent-weak);
  padding: 4px 12px;
  border-radius: 999px;
  font-variant-numeric: tabular-nums;
}
.quiz__question {
  margin: 0 0 18px;
  font-size: 1.25rem;
  font-weight: 600;
  line-height: 1.4;
  letter-spacing: -0.01em;
}

.quiz__options { list-style: none; margin: 0; padding: 0; display: grid; gap: 10px; }
.quiz__option {
  display: flex;
  align-items: center;
  gap: 12px;
  width: 100%;
  text-align: left;
  font: inherit;
  font-size: 1rem;
  background: var(--surface);
  border: 1.5px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 15px 16px;
  cursor: pointer;
  color: var(--ink);
  transition: border-color 0.18s var(--ease), background 0.18s var(--ease), transform 0.1s var(--ease);
}
.quiz__option:hover:not(:disabled) { border-color: var(--accent-weak); background: var(--accent-soft); }
.quiz__option:active:not(:disabled) { transform: scale(0.995); }
.quiz__option:disabled { cursor: default; }

.quiz__key {
  flex: 0 0 auto;
  width: 26px;
  height: 26px;
  border-radius: 8px;
  display: grid;
  place-items: center;
  font-size: 0.8rem;
  font-weight: 700;
  background: var(--bg);
  border: 1px solid var(--line);
  color: var(--ink-soft);
}
.quiz__option-text { flex: 1; }
.quiz__mark { flex: 0 0 auto; width: 20px; height: 20px; opacity: 0; transition: opacity 0.2s; }
.quiz__mark svg { width: 100%; height: 100%; fill: none; stroke-width: 2.4; stroke-linecap: round; stroke-linejoin: round; }

.quiz__option.is-correct {
  border-color: var(--ok);
  background: var(--ok-soft);
}
.quiz__option.is-correct .quiz__key { background: var(--ok); border-color: var(--ok); color: #fff; }
.quiz__option.is-correct .quiz__mark { opacity: 1; stroke: var(--ok); color: var(--ok); }
.quiz__option.is-wrong {
  border-color: var(--bad);
  background: var(--bad-soft);
}
.quiz__option.is-wrong .quiz__key { background: var(--bad); border-color: var(--bad); color: #fff; }
.quiz__option.is-wrong .quiz__mark { opacity: 1; stroke: var(--bad); color: var(--bad); }

.quiz__rationale {
  margin-top: 16px;
  background: var(--accent-soft);
  border: 1px solid var(--accent-weak);
  border-radius: var(--radius-sm);
  padding: 14px 16px;
  animation: fade-up 0.3s var(--ease);
}
.quiz__rationale-label {
  display: inline-block;
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  color: var(--accent);
  margin-bottom: 4px;
}
.quiz__rationale p { margin: 0; color: var(--ink-soft); font-size: 0.95rem; }

.quiz__controls { display: flex; justify-content: flex-end; margin-top: 20px; }

/* ---- Quiz summary ---- */
.quiz-summary {
  text-align: center;
  animation: fade-up 0.4s var(--ease);
}
.quiz-summary__score {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
  padding: 22px 0 8px;
}
.quiz-summary__big {
  font-size: 3rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  color: var(--accent);
  font-variant-numeric: tabular-nums;
  line-height: 1;
}
.quiz-summary__label { color: var(--ink-soft); font-size: 1rem; }

.quiz-summary__review {
  text-align: left;
  display: grid;
  gap: 12px;
  margin: 24px 0;
}
.review-item {
  background: var(--surface);
  border: 1px solid var(--line);
  border-left: 3px solid var(--bad);
  border-radius: var(--radius-sm);
  padding: 14px 16px;
}
.review-item__q { margin: 0 0 8px; font-weight: 600; font-size: 0.98rem; }
.review-item__row { margin: 0; font-size: 0.88rem; color: var(--ink-soft); }
.review-item__row + .review-item__row { margin-top: 3px; }
.review-item__yours { color: var(--bad); font-weight: 600; }
.review-item__correct { color: var(--ok); font-weight: 600; }
.review-item__rationale { margin-top: 8px; font-size: 0.88rem; color: var(--ink-soft); }
.quiz-summary__review-title {
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-faint);
  margin: 0 0 4px;
}
.quiz-summary__perfect {
  font-size: 1.05rem;
  color: var(--ok);
  font-weight: 600;
  margin: 0 0 8px;
}

/* ---------- Loading / error ---------- */
.loading, .error {
  text-align: center;
  padding: 40px 20px;
  color: var(--ink-faint);
}
.error { color: var(--bad); }

/* ---------- Footer ---------- */
.site-footer {
  border-top: 1px solid var(--line);
  margin-top: 48px;
  padding: 24px 0 36px;
}
.site-footer p { margin: 0; text-align: center; color: var(--ink-faint); font-size: 0.85rem; }
.site-footer a { color: var(--ink-soft); text-decoration: none; font-weight: 600; }
.site-footer a:hover { color: var(--accent); }

/* ---------- Focus visibility ---------- */
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.btn:focus-visible, .tab:focus-visible { outline-offset: 3px; }

/* ---------- Responsive ---------- */
@media (max-width: 480px) {
  .header-inner { padding-top: 12px; padding-bottom: 12px; }
  .brand__tag { display: none; }
  .intro { padding: 22px 0 6px; }
  .intro__title { font-size: 1.35rem; }
  .card { height: 300px; }
  .card__text { font-size: 1.1rem; }
  .card__face { padding: 24px 20px; }
  .fc__nav { width: 38px; height: 38px; }
  .quiz__question { font-size: 1.12rem; }
}

@media (max-width: 360px) {
  .wrap { padding: 0 14px; }
  .card { height: 280px; }
  .fc__controls .btn { padding: 10px 14px; }
}

@media (prefers-reduced-motion: reduce) {
  * { animation-duration: 0.001ms !important; transition-duration: 0.001ms !important; }
}