/* CSS Variables - Dark theme with accent */
:root {
  --bg-primary: #0f1419;
  --bg-secondary: #1a2332;
  --bg-card: #243447;
  --text-primary: #e7e9ea;
  --text-secondary: #8b98a5;
  --accent: #1d9bf0;
  --accent-hover: #1a8cd8;
  --correct: #00ba7c;
  --wrong: #f4212e;
  --border: #38444d;
  --font-sans: 'IBM Plex Sans', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  background: var(--bg-primary);
  color: var(--text-primary);
  min-height: 100vh;
  line-height: 1.6;
}

.app {
  max-width: 800px;
  margin: 0 auto;
  padding: 1.5rem;
  min-height: 100vh;
}

/* Screens */
.screen {
  display: none;
  animation: fadeIn 0.3s ease;
}

.screen.active {
  display: block;
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

/* Header */
.header {
  text-align: center;
  padding: 2rem 0;
}

.header h1 {
  font-size: 1.75rem;
  font-weight: 600;
  margin: 0;
  letter-spacing: -0.02em;
}

.subtitle {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-top: 0.25rem;
}

/* Welcome / Load */
.welcome-content {
  padding: 2rem 0;
}

.loader {
  text-align: center;
  padding: 3rem;
}

.loader p {
  color: var(--text-secondary);
  margin-top: 1rem;
}

.spinner {
  width: 48px;
  height: 48px;
  margin: 0 auto;
  border: 3px solid var(--border);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.error {
  text-align: center;
  padding: 2rem;
  background: rgba(244, 33, 46, 0.1);
  border: 1px solid var(--wrong);
  border-radius: 12px;
  color: var(--wrong);
}

.error code {
  display: block;
  margin: 1rem 0;
  padding: 0.75rem;
  background: var(--bg-secondary);
  border-radius: 8px;
  font-family: var(--font-mono);
  font-size: 0.9rem;
}

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

/* File selector */
.file-selector {
  margin-bottom: 1.5rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.file-selector label {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

.file-selector select {
  padding: 0.4rem 0.8rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-primary);
  border-radius: 6px;
  font-size: 0.9rem;
}

.btn-sm {
  padding: 0.35rem 0.75rem;
  font-size: 0.85rem;
}

/* Start panel */
.stats-cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
  margin-bottom: 2rem;
}

.stat-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.25rem;
  text-align: center;
}

.stat-card.highlight {
  border-color: var(--accent);
  background: rgba(29, 155, 240, 0.08);
}

.stat-value {
  display: block;
  font-size: 1.75rem;
  font-weight: 600;
}

.stat-label {
  font-size: 0.8rem;
  color: var(--text-secondary);
}

.action-buttons {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

/* Buttons */
.btn {
  padding: 0.75rem 1.5rem;
  border: none;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
}

.btn-primary {
  background: var(--accent);
  color: white;
}

.btn-primary:hover {
  background: var(--accent-hover);
}

.btn-secondary {
  background: var(--bg-card);
  color: var(--text-primary);
  border: 1px solid var(--border);
}

.btn-secondary:hover {
  background: var(--bg-secondary);
  border-color: var(--accent);
}

.btn-nav {
  background: var(--bg-card);
  color: var(--text-primary);
  border: 1px solid var(--border);
}

.btn-nav:hover:not(:disabled) {
  border-color: var(--accent);
}

.btn-nav:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.btn-icon {
  background: none;
  border: none;
  color: var(--text-primary);
  font-size: 1.25rem;
  cursor: pointer;
  padding: 0.5rem;
}

.btn-icon:hover {
  color: var(--accent);
}

/* Quiz screen */
.quiz-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.5rem 0 1rem;
  border-bottom: 1px solid var(--border);
}

.progress-info {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.quiz-content {
  padding: 1.5rem 0;
}

.question-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
}

.question-title {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin: 0 0 1rem;
  font-weight: 500;
}

.question-body {
  font-size: 1.05rem;
  margin-bottom: 1.5rem;
  white-space: pre-wrap;
}

.question-body p {
  margin: 0 0 0.5rem;
}

/* Options */
.options {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.option {
  display: flex;
  align-items: flex-start;
  gap: 0.75rem;
  padding: 1rem;
  background: var(--bg-card);
  border: 2px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.2s;
}

.option:hover {
  border-color: var(--accent);
  background: rgba(29, 155, 240, 0.05);
}

.option input {
  margin-top: 0.2rem;
  accent-color: var(--accent);
  cursor: pointer;
}

.option.selected {
  border-color: var(--accent);
  background: rgba(29, 155, 240, 0.1);
}

.option.correct {
  border-color: var(--correct);
  background: rgba(0, 186, 124, 0.1);
}

.option.wrong {
  border-color: var(--wrong);
  background: rgba(244, 33, 46, 0.1);
}

.option.disabled {
  pointer-events: none;
  opacity: 0.8;
}

.option.disabled:not(.correct):not(.wrong) {
  opacity: 0.6;
}

.option-label {
  font-weight: 600;
  min-width: 1.5rem;
}

.option-text {
  flex: 1;
}

/* Answer feedback */
.answer-feedback {
  margin-top: 1.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border);
}

.feedback-content {
  margin-bottom: 1rem;
  padding: 1rem;
  border-radius: 8px;
  font-weight: 500;
}

.feedback-content.correct-msg {
  background: rgba(0, 186, 124, 0.15);
  color: var(--correct);
}

.feedback-content.wrong-msg {
  background: rgba(244, 33, 46, 0.15);
  color: var(--wrong);
}

.quiz-nav {
  display: flex;
  justify-content: space-between;
  padding: 1rem 0;
  margin-top: 1rem;
}

/* Stats screen */
.stats-header {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border);
}

.stats-header h1 {
  font-size: 1.25rem;
  margin: 0;
}

.stats-content {
  padding: 1.5rem 0;
}

.overview-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(100px, 1fr));
  gap: 1rem;
  margin-bottom: 2rem;
}

.overview-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 1rem;
  text-align: center;
}

.overview-card.correct {
  border-color: var(--correct);
  background: rgba(0, 186, 124, 0.08);
}

.overview-card.wrong {
  border-color: var(--wrong);
  background: rgba(244, 33, 46, 0.08);
}

.overview-card.highlight {
  border-color: var(--accent);
  background: rgba(29, 155, 240, 0.08);
}

.overview-value {
  display: block;
  font-size: 1.5rem;
  font-weight: 600;
}

.overview-label {
  font-size: 0.75rem;
  color: var(--text-secondary);
}

.record-list h3 {
  font-size: 1rem;
  margin: 0 0 1rem;
}

.record-filters {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1rem;
}

.filter-btn {
  padding: 0.4rem 0.8rem;
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: var(--text-primary);
  border-radius: 6px;
  cursor: pointer;
  font-size: 0.85rem;
}

.filter-btn:hover {
  border-color: var(--accent);
}

.filter-btn.active {
  background: var(--accent);
  border-color: var(--accent);
}

.record-items {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.record-item {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 0.75rem;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 8px;
}

.record-item .status {
  width: 24px;
  height: 24px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.75rem;
  flex-shrink: 0;
}

.record-item .status.correct {
  background: var(--correct);
  color: white;
}

.record-item .status.wrong {
  background: var(--wrong);
  color: white;
}

.record-item .status.unanswered {
  background: var(--border);
  color: var(--text-secondary);
}

.record-item .title {
  flex: 1;
}

.record-item .goto-btn {
  padding: 0.3rem 0.6rem;
  font-size: 0.8rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-primary);
  border-radius: 4px;
  cursor: pointer;
}

.record-item .goto-btn:hover {
  border-color: var(--accent);
}

@media (max-width: 600px) {
  .stats-cards {
    grid-template-columns: 1fr;
  }
  
  .action-buttons {
    flex-direction: column;
  }
  
  .btn {
    width: 100%;
  }
}