:root {
  color-scheme: light;
  --bg: #f3f6fb;
  --panel: #ffffff;
  --text: #18243a;
  --muted: #627188;
  --border: #dfe5ee;
  --primary: #315fe5;
  --primary-hover: #254fc7;
  --soft: #f5f7fb;
  --success: #187244;
  --success-bg: #e8f7ed;
  --success-border: #8dd2a6;
  --danger: #ad3340;
  --danger-bg: #fff0f1;
  --danger-border: #e9a3aa;
  --shadow: 0 14px 50px rgba(24, 36, 58, 0.07);
}

@media (prefers-color-scheme: dark) {
  :root {
    color-scheme: dark;
    --bg: #101824;
    --panel: #192537;
    --text: #f0f4fb;
    --muted: #b4c0d0;
    --border: #364459;
    --primary: #7194ff;
    --primary-hover: #94adff;
    --soft: #243246;
    --success: #78dfa1;
    --success-bg: #183d2c;
    --success-border: #40865b;
    --danger: #ff98a0;
    --danger-bg: #48262d;
    --danger-border: #ad636d;
    --shadow: 0 14px 50px rgba(0, 0, 0, 0.2);
  }
}

* {
  box-sizing: border-box;
}

[hidden] {
  display: none !important;
}

body {
  margin: 0;
  min-height: 100vh;
  background: var(--bg);
  color: var(--text);
  font-family: system-ui, -apple-system, BlinkMacSystemFont,
               "Segoe UI", sans-serif;
  line-height: 1.5;
}

button, input {
  font: inherit;
}

button, label {
  -webkit-tap-highlight-color: transparent;
}

button:focus-visible,
label:focus-within,
input:focus-visible,
h2:focus-visible {
  outline: 3px solid var(--primary);
  outline-offset: 3px;
}

.app {
  width: min(100% - 32px, 800px);
  margin: 36px auto;
}

.header {
  margin-bottom: 28px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 16px;
}

.brand-icon {
  display: grid;
  place-items: center;
  width: 52px;
  height: 52px;
  border-radius: 16px;
  background: var(--primary);
  color: #fff;
  font-size: 30px;
  font-weight: 800;
}

.brand h1 {
  margin: 0;
  font-size: 25px;
  letter-spacing: -0.6px;
}

.brand p {
  margin: 2px 0 0;
  color: var(--muted);
  font-size: 14px;
}

.panel {
  padding: clamp(22px, 5vw, 42px);
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 22px;
  box-shadow: var(--shadow);
}

.section-header {
  margin-bottom: 24px;
}

.eyebrow {
  display: inline-block;
  color: var(--primary);
  font-size: 12px;
  font-weight: 800;
  letter-spacing: 1.25px;
}

.section-header h2,
.results-header h2 {
  margin: 9px 0;
  font-size: clamp(24px, 4vw, 32px);
  letter-spacing: -0.8px;
}

.section-header p,
.results-header p {
  margin: 0;
  color: var(--muted);
}

.notice {
  padding: 13px 16px;
  margin-bottom: 22px;
  background: var(--soft);
  border: 1px solid var(--border);
  border-radius: 10px;
  color: var(--muted);
  font-size: 14px;
  overflow-wrap: anywhere;
}

.notice[data-kind="success"] {
  color: var(--success);
  background: var(--success-bg);
  border-color: var(--success-border);
}

.notice[data-kind="warning"] {
  color: var(--danger);
  background: var(--danger-bg);
  border-color: var(--danger-border);
}

.set-fieldset {
  border: 0;
  padding: 0;
  margin: 0;
  min-width: 0;
}

.set-grid {
  display: grid;
  gap: 12px;
}

.set-card {
  display: flex;
  align-items: flex-start;
  gap: 13px;
  padding: 18px;
  cursor: pointer;
  border: 2px solid var(--border);
  border-radius: 13px;
  transition: border-color 150ms, background 150ms;
}

.set-card:hover {
  border-color: var(--primary);
}

.set-card:has(input:checked) {
  background: var(--soft);
  border-color: var(--primary);
}

.set-card input {
  margin-top: 5px;
  accent-color: var(--primary);
}

.set-card-body {
  display: grid;
  min-width: 0;
  gap: 3px;
}

.set-card-title {
  font-weight: 700;
  overflow-wrap: anywhere;
}

.set-card-description {
  color: var(--muted);
  font-size: 14px;
  overflow-wrap: anywhere;
}

.set-card-meta {
  color: var(--muted);
  font-size: 12px;
}

.upload-panel {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  margin: 25px 0;
  padding: 20px;
  background: var(--soft);
  border: 1px dashed var(--border);
  border-radius: 12px;
}

.upload-panel h3 {
  margin: 0 0 5px;
  font-size: 16px;
}

.upload-panel p {
  margin: 0;
  font-size: 13px;
  color: var(--muted);
}

.file-input {
  position: absolute;
  width: 1px;
  height: 1px;
  opacity: 0;
  overflow: hidden;
}

.btn {
  display: inline-flex;
  justify-content: center;
  align-items: center;
  gap: 10px;
  padding: 12px 19px;
  border: 1px solid transparent;
  border-radius: 10px;
  font-size: 14px;
  font-weight: 700;
  text-align: center;
  text-decoration: none;
  cursor: pointer;
  transition: background 150ms, opacity 150ms;
}

.btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.btn-primary {
  background: var(--primary);
  color: #fff;
}

@media (prefers-color-scheme: dark) {
  .btn-primary {
    color: #101824;
  }
}

.btn-primary:not(:disabled):hover {
  background: var(--primary-hover);
}

.btn-secondary {
  background: var(--panel);
  color: var(--text);
  border-color: var(--border);
}

.btn-secondary:hover {
  background: var(--soft);
}

.btn-danger-outline {
  background: transparent;
  color: var(--danger);
  border-color: var(--danger-border);
}

.btn-danger-outline:hover {
  background: var(--danger-bg);
}

.btn-full {
  width: 100%;
}

.quiz-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.quiz-set-name {
  margin: 4px 0 0;
  font-size: 19px;
  overflow-wrap: anywhere;
}

.stats-bar {
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 26px;
  color: var(--muted);
  font-size: 13px;
  font-weight: 600;
}

.progress {
  height: 7px;
  margin: 12px 0 33px;
  background: var(--soft);
  border-radius: 20px;
  overflow: hidden;
}

.progress-fill {
  width: 0;
  height: 100%;
  background: var(--primary);
  border-radius: 20px;
  transition: width 200ms;
}

.question-block h2 {
  margin: 0 0 10px;
  font-size: clamp(21px, 3.5vw, 28px);
  line-height: 1.35;
  letter-spacing: -0.3px;
}

.keyboard-hint {
  color: var(--muted);
  margin: 0 0 24px;
  font-size: 13px;
}

.answers {
  display: grid;
  gap: 11px;
}

.answer {
  display: flex;
  align-items: center;
  gap: 14px;
  width: 100%;
  min-height: 64px;
  padding: 13px 16px;
  text-align: left;
  border: 2px solid var(--border);
  border-radius: 12px;
  background: var(--panel);
  color: var(--text);
  cursor: pointer;
  transition: border-color 150ms, background 150ms;
}

.answer:not(:disabled):hover {
  background: var(--soft);
  border-color: var(--primary);
}

.answer:disabled {
  cursor: default;
  opacity: 1;
}

.answer-letter {
  display: grid;
  flex: 0 0 34px;
  place-items: center;
  width: 34px;
  height: 34px;
  background: var(--soft);
  border-radius: 8px;
  font-weight: 800;
}

.answer-text {
  flex: 1;
  min-width: 0;
  overflow-wrap: anywhere;
}

.answer-symbol {
  font-size: 23px;
  font-weight: 800;
}

.answer.is-correct {
  background: var(--success-bg);
  border-color: var(--success-border);
  color: var(--success);
}

.answer.is-wrong {
  background: var(--danger-bg);
  border-color: var(--danger-border);
  color: var(--danger);
}

.answer.is-dimmed {
  opacity: 0.65;
}

.feedback {
  margin-top: 20px;
  padding: 16px 18px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--soft);
}

.feedback.is-correct {
  color: var(--success);
  background: var(--success-bg);
  border-color: var(--success-border);
}

.feedback.is-wrong {
  color: var(--danger);
  background: var(--danger-bg);
  border-color: var(--danger-border);
}

.feedback p {
  margin: 7px 0 0;
  font-size: 14px;
  line-height: 1.6;
}

.quiz-actions {
  display: flex;
  justify-content: flex-end;
  margin-top: 28px;
}

.results-header {
  text-align: center;
}

.trophy {
  display: grid;
  place-items: center;
  width: 64px;
  height: 64px;
  margin: 0 auto 15px;
  border-radius: 20px;
  background: var(--success-bg);
  color: var(--success);
  font-size: 36px;
}

.score-hero {
  display: grid;
  justify-items: center;
  margin: 30px 0;
  gap: 3px;
}

.score-hero strong {
  color: var(--success);
  font-size: clamp(50px, 10vw, 76px);
  line-height: 1.2;
  font-variant-numeric: tabular-nums;
}

.score-hero span {
  color: var(--muted);
  font-size: 14px;
}

.result-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 12px;
}

.result-card {
  display: grid;
  justify-items: center;
  gap: 6px;
  padding: 16px 8px;
  border-radius: 12px;
  background: var(--soft);
  text-align: center;
}

.result-card strong {
  font-size: 27px;
  font-variant-numeric: tabular-nums;
}

.result-card span {
  color: var(--muted);
  font-size: 12px;
}

.success-text {
  color: var(--success);
}

.danger-text {
  color: var(--danger);
}

.first-attempt {
  display: flex;
  justify-content: space-between;
  gap: 15px;
  margin-top: 24px;
  padding: 16px 0;
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}

.first-attempt strong {
  color: var(--primary);
  font-size: 20px;
}

.results-note {
  margin: 14px 0 25px;
  color: var(--muted);
  font-size: 13px;
}

.results-actions {
  display: flex;
  gap: 12px;
}

.results-actions .btn {
  flex: 1;
}

.footer {
  padding: 22px;
  color: var(--muted);
  text-align: center;
  font-size: 12px;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

@media (max-width: 600px) {
  .app {
    width: min(100% - 20px, 800px);
    margin: 15px auto;
  }

  .panel {
    border-radius: 15px;
  }

  .upload-panel,
  .results-actions {
    flex-direction: column;
    align-items: stretch;
  }

  .result-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .quiz-actions .btn {
    width: 100%;
  }

  .brand h1 {
    font-size: 21px;
  }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
  }
}