:root {
  --bg: #f6f8fb;
  --card: #ffffff;
  --text: #15233a;
  --muted: #6b7a90;
  --primary: #4f7df9;
  --primary-dark: #3863dc;
  --primary-soft: #eaf0ff;
  --success: #1f9d55;
  --success-soft: #e6f6ec;
  --danger: #e34850;
  --danger-soft: #fdebec;
  --border: #e6ebf3;
  --shadow: 0 4px 16px rgba(15, 36, 80, 0.06);
  --shadow-lg: 0 12px 40px rgba(15, 36, 80, 0.12);
  --radius: 14px;
  --radius-sm: 8px;
  --transition: 180ms cubic-bezier(.2,.8,.2,1);

  --idiom-grad-start: #fff7e6;
  --idiom-grad-end: #ffffff;
  --idiom-border: #ffd591;
  --idiom-text: #cc7a00;
  --flash-front-start: #f0f5ff;
  --flash-front-end: #ffffff;
  --flash-back-start: #e6f6ec;
  --flash-back-end: #ffffff;
  --flash-back-border: #b8e0c8;
}

[data-theme="dark"] {
  --bg: #0f1623;
  --card: #1a2336;
  --text: #e6ecf5;
  --muted: #8b9bb5;
  --primary: #6e9bff;
  --primary-dark: #4f7df9;
  --primary-soft: #1e2a47;
  --success: #4ade80;
  --success-soft: #14361f;
  --danger: #f87171;
  --danger-soft: #3a1518;
  --border: #2a3548;
  --shadow: 0 4px 16px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0 12px 40px rgba(0, 0, 0, 0.45);

  --idiom-grad-start: #2c2317;
  --idiom-grad-end: #1a2336;
  --idiom-border: #6b4f1c;
  --idiom-text: #ffc873;
  --flash-front-start: #1c2a47;
  --flash-front-end: #1a2336;
  --flash-back-start: #163524;
  --flash-back-end: #1a2336;
  --flash-back-border: #2f6342;
}

html { transition: background-color 200ms ease, color 200ms ease; }

/* Lucide icons */
[data-lucide] {
  width: 20px;
  height: 20px;
  stroke-width: 2;
  vertical-align: middle;
  display: inline-block;
}
.inline-icon { width: 16px; height: 16px; vertical-align: -3px; margin-right: 2px; }
.logo [data-lucide] { width: 22px; height: 22px; color: var(--primary); }
.ghost-btn [data-lucide] { width: 18px; height: 18px; }
.mode-icon [data-lucide] { width: 32px; height: 32px; color: var(--primary); }
.result-emoji [data-lucide] { width: 64px; height: 64px; color: var(--primary); stroke-width: 1.5; }
.feedback [data-lucide] { color: inherit; }
.unit-card.idioms [data-lucide] { color: var(--idiom-text); }

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

body { min-height: 100vh; display: flex; flex-direction: column; }

/* Topbar */
.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  background: var(--card);
  border-bottom: 1px solid var(--border);
  padding: 12px 20px;
  display: flex;
  align-items: center;
  gap: 16px;
}

.brand { display: flex; align-items: center; gap: 8px; cursor: pointer; user-select: none; }
.logo { font-size: 22px; }
.brand-name { font-weight: 700; font-size: 16px; letter-spacing: 0.2px; }

.crumbs {
  flex: 1;
  display: flex;
  align-items: center;
  gap: 6px;
  color: var(--muted);
  font-size: 13px;
  overflow-x: auto;
  white-space: nowrap;
}
.crumbs .crumb { padding: 4px 10px; border-radius: 999px; background: var(--bg); }
.crumbs .crumb.clickable { cursor: pointer; transition: background var(--transition); }
.crumbs .crumb.clickable:hover { background: var(--primary-soft); color: var(--primary); }
.crumbs .sep { opacity: 0.5; }

.ghost-btn {
  background: transparent;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  width: 36px;
  height: 36px;
  font-size: 18px;
  cursor: pointer;
  color: var(--text);
  transition: all var(--transition);
}
.ghost-btn:hover { background: var(--primary-soft); border-color: var(--primary); color: var(--primary); }

/* Main */
main {
  flex: 1;
  width: 100%;
  max-width: 1100px;
  margin: 0 auto;
  padding: 32px 20px 64px;
}

.screen { animation: fadeIn 240ms ease; }
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

h1 { font-size: 28px; margin: 0 0 8px; letter-spacing: -0.3px; }
h3 { margin: 0; }
.muted { color: var(--muted); margin: 0 0 24px; }

/* Grids */
.grid { display: grid; gap: 16px; }
.grid-levels { grid-template-columns: repeat(auto-fill, minmax(180px, 1fr)); }
.grid-units { grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); }
.grid-modes { grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); }

.card, .mode-card, .level-card, .unit-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px 20px;
  cursor: pointer;
  transition: all var(--transition);
  text-align: left;
  font-family: inherit;
  font-size: 14px;
  color: inherit;
  box-shadow: var(--shadow);
}
.card:hover, .mode-card:hover, .level-card:hover, .unit-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
  border-color: var(--primary);
}

.level-card { display: flex; flex-direction: column; gap: 8px; align-items: flex-start; }
.level-badge {
  font-size: 22px;
  font-weight: 700;
  background: var(--primary-soft);
  color: var(--primary);
  padding: 6px 14px;
  border-radius: var(--radius-sm);
  letter-spacing: 0.5px;
}
.level-card .count { color: var(--muted); font-size: 13px; }

.unit-card { display: flex; flex-direction: column; gap: 6px; }
.unit-card .unit-title { font-size: 16px; font-weight: 600; }
.unit-card .unit-count { color: var(--muted); font-size: 13px; }
.unit-card.idioms { background: linear-gradient(135deg, var(--idiom-grad-start), var(--idiom-grad-end)); border-color: var(--idiom-border); }
.unit-card.idioms .unit-count { color: var(--idiom-text); }

.mode-card { display: flex; flex-direction: column; gap: 8px; }
.mode-icon { font-size: 28px; }
.mode-card h3 { font-size: 16px; }
.mode-card p { margin: 0; color: var(--muted); font-size: 13px; }

/* Quiz */
.quiz-screen { max-width: 640px; margin: 0 auto; }

.quiz-header { margin-bottom: 24px; }
.progress {
  height: 8px;
  background: var(--border);
  border-radius: 999px;
  overflow: hidden;
  margin-bottom: 10px;
}
.progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), #6e9bff);
  width: 0;
  transition: width 320ms ease;
}
.quiz-stats {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 13px;
  color: var(--muted);
}
.quiz-stats .dot { width: 4px; height: 4px; background: var(--border); border-radius: 50%; }
.score-pos { color: var(--success); font-weight: 600; }
.score-neg { color: var(--danger); font-weight: 600; }

.quiz-body {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px 24px;
  box-shadow: var(--shadow);
  min-height: 280px;
}

.q-prompt-label {
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.6px;
  color: var(--muted);
  font-weight: 600;
  margin-bottom: 8px;
}
.q-prompt {
  font-size: 26px;
  font-weight: 600;
  margin-bottom: 24px;
  line-height: 1.3;
}

.options { display: flex; flex-direction: column; gap: 10px; }
.option {
  background: var(--card);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 14px 16px;
  cursor: pointer;
  text-align: left;
  font-family: inherit;
  font-size: 15px;
  color: var(--text);
  transition: all 120ms ease;
  display: flex;
  align-items: center;
  gap: 12px;
}
.option:hover:not(:disabled) { border-color: var(--primary); background: var(--primary-soft); }
.option .opt-letter {
  background: var(--bg);
  border-radius: 50%;
  width: 26px;
  height: 26px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-weight: 600;
  font-size: 13px;
  flex-shrink: 0;
}
.option.correct { background: var(--success-soft); border-color: var(--success); color: var(--success); }
.option.correct .opt-letter { background: var(--success); color: white; }
.option.wrong { background: var(--danger-soft); border-color: var(--danger); color: var(--danger); }
.option.wrong .opt-letter { background: var(--danger); color: white; }
.option:disabled { cursor: default; }

.type-input {
  width: 100%;
  padding: 14px 16px;
  font-size: 17px;
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  font-family: inherit;
  background: var(--card);
  color: var(--text);
  outline: none;
  transition: border-color var(--transition);
}
.type-input:focus { border-color: var(--primary); box-shadow: 0 0 0 3px var(--primary-soft); }
.type-input.correct { border-color: var(--success); background: var(--success-soft); }
.type-input.wrong { border-color: var(--danger); background: var(--danger-soft); }

.feedback {
  margin-top: 14px;
  padding: 10px 14px;
  border-radius: var(--radius-sm);
  font-size: 14px;
}
.feedback.ok { background: var(--success-soft); color: var(--success); }
.feedback.no { background: var(--danger-soft); color: var(--danger); }
.feedback strong { font-weight: 700; }

/* Flashcard */
.flashcard {
  perspective: 1000px;
  height: 280px;
  cursor: pointer;
}
.flashcard-inner {
  position: relative;
  width: 100%;
  height: 100%;
  transition: transform 480ms;
  transform-style: preserve-3d;
}
.flashcard.flipped .flashcard-inner { transform: rotateY(180deg); }
.flashcard-face {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius);
  padding: 24px;
  text-align: center;
}
.flashcard-front {
  background: linear-gradient(135deg, var(--flash-front-start), var(--flash-front-end));
  border: 1.5px solid var(--primary-soft);
}
.flashcard-back {
  background: linear-gradient(135deg, var(--flash-back-start), var(--flash-back-end));
  border: 1.5px solid var(--flash-back-border);
  transform: rotateY(180deg);
}
.flashcard-label {
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.8px;
  color: var(--muted);
  margin-bottom: 12px;
  font-weight: 600;
}
.flashcard-text { font-size: 28px; font-weight: 600; line-height: 1.3; }
.flashcard-hint {
  position: absolute;
  bottom: 16px;
  font-size: 12px;
  color: var(--muted);
}

/* Buttons */
.quiz-footer {
  display: flex;
  gap: 10px;
  margin-top: 18px;
  flex-wrap: wrap;
  justify-content: space-between;
}
.primary-btn, .secondary-btn {
  padding: 12px 22px;
  border-radius: var(--radius-sm);
  border: none;
  font-family: inherit;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition);
}
.primary-btn { background: var(--primary); color: white; }
.primary-btn:hover { background: var(--primary-dark); }
.secondary-btn { background: var(--card); color: var(--text); border: 1.5px solid var(--border); }
.secondary-btn:hover { border-color: var(--primary); color: var(--primary); }
.flash-controls { display: flex; gap: 10px; }

/* Results */
.results-screen { max-width: 520px; margin: 0 auto; text-align: center; }
.result-emoji { font-size: 72px; margin: 12px 0; }
.results-screen h1 { font-size: 32px; margin-bottom: 8px; }
.result-score { margin: 24px 0 32px; }
.big-score { font-size: 48px; font-weight: 700; }
.result-pct { font-size: 20px; color: var(--muted); margin-top: 4px; }
.result-actions { display: flex; gap: 10px; flex-wrap: wrap; justify-content: center; }

.mistakes {
  margin-top: 32px;
  text-align: left;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 20px;
}
.mistakes summary { cursor: pointer; font-weight: 600; padding: 4px 0; }
.mistakes ul { margin: 12px 0 0; padding-left: 18px; }
.mistakes li { margin-bottom: 8px; font-size: 14px; }
.mistakes .ans-tr { color: var(--text); font-weight: 600; }
.mistakes .ans-uz { color: var(--muted); }

@media (max-width: 600px) {
  .topbar { padding: 10px 14px; }
  main { padding: 20px 14px 48px; }
  h1 { font-size: 22px; }
  .q-prompt { font-size: 22px; }
  .flashcard { height: 240px; }
  .flashcard-text { font-size: 22px; }
  .big-score { font-size: 38px; }
}