/* ==========================================================================
   Java Technical Revision Portal - Engineering Design System
   Strict 8pt Rhythm | Zero Vibe-Coded Anti-Patterns | Intentional Layout
   ========================================================================== */

:root {
  /* 1. Strict Spacing Rhythm (8-Point Scale) */
  --space-4: 4px;
  --space-8: 8px;
  --space-12: 12px;
  --space-16: 16px;
  --space-24: 24px;
  --space-32: 32px;
  --space-40: 40px;
  --space-48: 48px;
  --space-64: 64px;

  /* 2. Disciplined Palette: One dominant neutral, one accent, restrained contrast.
        Rule 1 & Rule 4: No neon saturation, no purple gradients. */
  --bg-page: #0d1117;
  --bg-surface: #161b22;
  --bg-surface-elevated: #21262d;
  --bg-input: #0d1117;

  --border-default: #30363d;
  --border-subtle: #21262d;
  --border-focus: #58a6ff;

  --text-primary: #f0f6fc;
  --text-secondary: #8b949e;
  --text-tertiary: #6e7681;

  --color-accent: #1f6feb;
  --color-accent-hover: #388bfd;
  --color-accent-subtle: rgba(56, 139, 253, 0.12);

  /* Semantic, actionable status tokens (Rule 7: Every status maps to a real state) */
  --status-mastered-text: #3fb950;
  --status-mastered-bg: rgba(46, 160, 67, 0.15);
  --status-mastered-border: rgba(46, 160, 67, 0.4);

  --status-review-text: #d29922;
  --status-review-bg: rgba(187, 128, 9, 0.15);
  --status-review-border: rgba(187, 128, 9, 0.4);

  --status-unrated-text: #8b949e;
  --status-unrated-bg: rgba(110, 118, 129, 0.1);
  --status-unrated-border: rgba(110, 118, 129, 0.25);

  --color-danger: #f85149;

  /* 3. Typography System */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

  --text-xs: 12px;
  --text-sm: 14px;
  --text-base: 16px;
  --text-lg: 18px;
  --text-xl: 20px;
  --text-2xl: 24px;

  --leading-tight: 1.25;
  --leading-normal: 1.5;
  --leading-relaxed: 1.625;

  /* 4. Unified Geometry (Rule 2: No decorative glows or radial blooms) */
  --radius-sm: 6px;
  --radius-md: 8px;
  --radius-lg: 12px;

  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
  --shadow-modal: 0 16px 32px rgba(0, 0, 0, 0.6);

  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-normal: 220ms cubic-bezier(0.4, 0, 0.2, 1);
}

/* Base Reset */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  /* Rule 2: Pure disciplined solid surface. Zero radial aurora borealis glows. */
  background-color: var(--bg-page);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: var(--text-sm);
  line-height: var(--leading-normal);
  -webkit-font-smoothing: antialiased;
  min-height: 100vh;
}

/* --------------------------------------------------------------------------
   HEADER & NAVIGATION
   -------------------------------------------------------------------------- */
.app-header {
  background-color: var(--bg-surface);
  border-bottom: 1px solid var(--border-default);
  padding: var(--space-16) var(--space-32);
  position: sticky;
  top: 0;
  z-index: 40;
}

.header-container {
  max-width: 1120px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-16);
  flex-wrap: wrap;
}

.brand-group {
  display: flex;
  align-items: center;
  gap: var(--space-12);
}

.brand-mark {
  width: 32px;
  height: 32px;
  background-color: var(--color-accent);
  color: #ffffff;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  font-weight: 700;
}

.brand-text {
  display: flex;
  flex-direction: column;
}

.brand-title {
  font-size: var(--text-base);
  font-weight: 600;
  color: var(--text-primary);
  line-height: var(--leading-tight);
}

.brand-subtitle {
  font-size: var(--text-xs);
  color: var(--text-secondary);
  line-height: var(--leading-tight);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-8);
}

/* --------------------------------------------------------------------------
   BUTTON SYSTEM
   -------------------------------------------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-8);
  height: 36px;
  padding: 0 var(--space-12);
  border-radius: var(--radius-md);
  font-family: var(--font-sans);
  font-size: var(--text-sm);
  font-weight: 500;
  cursor: pointer;
  border: 1px solid transparent;
  transition: background-color var(--transition-fast), border-color var(--transition-fast), color var(--transition-fast);
  user-select: none;
  white-space: nowrap;
}

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

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

.btn-secondary {
  background-color: var(--bg-surface-elevated);
  border-color: var(--border-default);
  color: var(--text-primary);
}

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

/* --------------------------------------------------------------------------
   MAIN LAYOUT & STATS
   Rule 5: Avoid wrapping everything in cards within cards.
   We use clean typographic proximity and whitespace for the stats overview.
   -------------------------------------------------------------------------- */
.main-layout {
  max-width: 1120px;
  margin: 0 auto;
  padding: var(--space-32);
}

.stats-row {
  display: flex;
  align-items: baseline;
  gap: var(--space-48);
  padding: var(--space-16) 0 var(--space-24) 0;
  border-bottom: 1px solid var(--border-default);
  margin-bottom: var(--space-24);
  flex-wrap: wrap;
}

.stat-item {
  display: flex;
  align-items: baseline;
  gap: var(--space-8);
}

.stat-value {
  font-size: var(--text-2xl);
  font-weight: 700;
  font-family: var(--font-mono);
  color: var(--text-primary);
  line-height: 1;
}

.stat-value.mastered { color: var(--status-mastered-text); }
.stat-value.review { color: var(--status-review-text); }

.stat-label {
  font-size: var(--text-xs);
  font-weight: 500;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

/* --------------------------------------------------------------------------
   CONTROLS BAR
   Rule 5: Uses layout grouping and whitespace instead of a bulky nested box.
   -------------------------------------------------------------------------- */
.controls-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-16);
  margin-bottom: var(--space-24);
  flex-wrap: wrap;
}

.search-field {
  flex: 1;
  min-width: 280px;
  position: relative;
  display: flex;
  align-items: center;
}

.search-icon {
  position: absolute;
  left: var(--space-12);
  color: var(--text-tertiary);
  pointer-events: none;
}

.input-text {
  width: 100%;
  height: 36px;
  background-color: var(--bg-input);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  padding: 0 var(--space-12) 0 36px;
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: var(--text-sm);
  transition: border-color var(--transition-fast);
}

.input-text:focus {
  outline: none;
  border-color: var(--border-focus);
}

.filters-group {
  display: flex;
  align-items: center;
  gap: var(--space-8);
  flex-wrap: wrap;
}

.select-field {
  height: 36px;
  background-color: var(--bg-input);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: var(--text-sm);
  padding: 0 var(--space-12);
  cursor: pointer;
}

.select-field:focus {
  outline: none;
  border-color: var(--border-focus);
}

/* --------------------------------------------------------------------------
   ACCORDION SYSTEM
   Rule 5 & Rule 6: No card-in-card nesting, no multicolored rainbow side tabs.
   -------------------------------------------------------------------------- */
.accordion-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-12);
}

.accordion-item {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: border-color var(--transition-fast);
}

.accordion-item:hover {
  border-color: var(--text-secondary);
}

.accordion-header {
  padding: var(--space-16) var(--space-24);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-16);
  cursor: pointer;
  user-select: none;
}

.question-meta {
  display: flex;
  flex-direction: column;
  gap: var(--space-8);
  flex: 1;
}

.badges-row {
  display: flex;
  align-items: center;
  gap: var(--space-8);
  flex-wrap: wrap;
}

.tag {
  font-size: var(--text-xs);
  font-weight: 500;
  padding: 2px var(--space-8);
  border-radius: var(--radius-sm);
  line-height: var(--leading-normal);
}

.tag-category {
  background-color: var(--color-accent-subtle);
  color: #58a6ff;
  border: 1px solid rgba(88, 166, 255, 0.25);
}

.tag-difficulty {
  background-color: var(--bg-surface-elevated);
  color: var(--text-secondary);
  border: 1px solid var(--border-default);
}

.tag-custom {
  background-color: rgba(110, 118, 129, 0.15);
  color: var(--text-secondary);
  border: 1px solid var(--border-default);
}

.question-title {
  font-size: var(--text-base);
  font-weight: 500;
  color: var(--text-primary);
  line-height: var(--leading-normal);
}

.header-controls {
  display: flex;
  align-items: center;
  gap: var(--space-8);
}

/* Interactive Actionable Status Badge Pill (Rule 7: Maps to actual user state) */
.status-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-4);
  height: 28px;
  padding: 0 var(--space-8);
  border-radius: var(--radius-sm);
  font-size: var(--text-xs);
  font-weight: 500;
  cursor: pointer;
  border: 1px solid transparent;
  transition: background-color var(--transition-fast), border-color var(--transition-fast);
}

.status-badge.unrated {
  background-color: var(--status-unrated-bg);
  border-color: var(--status-unrated-border);
  color: var(--status-unrated-text);
}

.status-badge.needs_review {
  background-color: var(--status-review-bg);
  border-color: var(--status-review-border);
  color: var(--status-review-text);
}

.status-badge.mastered {
  background-color: var(--status-mastered-bg);
  border-color: var(--status-mastered-border);
  color: var(--status-mastered-text);
}

.accordion-chevron {
  color: var(--text-tertiary);
  transition: transform var(--transition-normal);
}

.accordion-item.expanded .accordion-chevron {
  transform: rotate(180deg);
}

/* Accordion Content Body */
.accordion-content {
  max-height: 0;
  overflow: hidden;
  transition: max-height var(--transition-normal);
  border-top: 1px solid transparent;
}

.accordion-item.expanded .accordion-content {
  border-top-color: var(--border-default);
}

.answer-container {
  padding: var(--space-24);
  color: var(--text-secondary);
  font-size: var(--text-sm);
  line-height: var(--leading-relaxed);
}

.answer-container h3, .answer-container h4 {
  color: var(--text-primary);
  font-weight: 600;
  margin: var(--space-16) 0 var(--space-8) 0;
}

.answer-container h3:first-child { margin-top: 0; }

.answer-container p {
  margin-bottom: var(--space-12);
}

.answer-container ul, .answer-container ol {
  margin: var(--space-8) 0 var(--space-16) var(--space-24);
}

.answer-container li {
  margin-bottom: var(--space-4);
}

/* Tables in answers */
.answer-container table {
  width: 100%;
  border-collapse: collapse;
  margin: var(--space-16) 0;
  font-size: var(--text-xs);
}

.answer-container th, .answer-container td {
  border: 1px solid var(--border-default);
  padding: var(--space-8) var(--space-12);
  text-align: left;
}

.answer-container th {
  background-color: var(--bg-surface-elevated);
  color: var(--text-primary);
  font-weight: 600;
}

/* Code Blocks */
.answer-container pre {
  background-color: #080c14;
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  padding: var(--space-16);
  overflow-x: auto;
  margin: var(--space-16) 0;
}

.answer-container code {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
}

.answer-container p code, .answer-container li code {
  background-color: var(--bg-surface-elevated);
  border: 1px solid var(--border-default);
  color: #79c0ff;
  padding: 2px var(--space-4);
  border-radius: 4px;
}

/* --------------------------------------------------------------------------
   DIALOG MODALS
   -------------------------------------------------------------------------- */
dialog {
  border: 1px solid var(--border-default);
  background-color: var(--bg-surface);
  color: var(--text-primary);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-modal);
  max-width: 560px;
  width: 100%;
  margin: auto;
  padding: 0;
}

dialog::backdrop {
  background-color: rgba(0, 0, 0, 0.75);
}

.modal-header {
  padding: var(--space-16) var(--space-24);
  border-bottom: 1px solid var(--border-default);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.modal-title {
  font-size: var(--text-base);
  font-weight: 600;
}

.btn-icon {
  background: none;
  border: none;
  color: var(--text-tertiary);
  cursor: pointer;
  padding: var(--space-4);
  display: flex;
  align-items: center;
}

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

.modal-body {
  padding: var(--space-24);
}

.form-group {
  margin-bottom: var(--space-16);
}

.form-label {
  display: block;
  font-size: var(--text-xs);
  font-weight: 500;
  color: var(--text-secondary);
  margin-bottom: var(--space-8);
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

.form-input, .form-textarea, .form-select {
  width: 100%;
  background-color: var(--bg-input);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  padding: var(--space-8) var(--space-12);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: var(--text-sm);
}

.form-textarea {
  min-height: 140px;
  resize: vertical;
  line-height: var(--leading-relaxed);
}

.form-input:focus, .form-textarea:focus, .form-select:focus {
  outline: none;
  border-color: var(--border-focus);
}

.modal-footer {
  padding: var(--space-16) var(--space-24);
  border-top: 1px solid var(--border-default);
  display: flex;
  justify-content: flex-end;
  gap: var(--space-8);
}

/* Prompt display box */
.prompt-box {
  background-color: #080c14;
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  padding: var(--space-16);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: #79c0ff;
  user-select: all;
  white-space: pre-wrap;
  margin-bottom: var(--space-16);
  line-height: var(--leading-relaxed);
}

/* Empty State */
.empty-state {
  text-align: center;
  padding: var(--space-64) var(--space-16);
  color: var(--text-tertiary);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-8);
}