/* ==========================================================================
   IUPAC Komplex-Nomenklatur Web App - Modern Stylesheet
   Designed for School & Chemistry Olympiad (ÖChO)
   ========================================================================== */

:root {
  --font-sans: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, "Cascadia Code", "Source Code Pro", Menlo, Consolas, monospace;

  /* Color Palette - Light Mode */
  --bg-page: #f8fafc;
  --bg-card: #ffffff;
  --bg-card-subtle: #f1f5f9;
  --bg-card-alt: #f8fafc;
  --border-color: #cbd5e1;
  --border-color-subtle: #e2e8f0;

  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #64748b;
  --text-inverse: #ffffff;

  --brand-blue: #1e40af;
  --brand-blue-hover: #1d4ed8;
  --brand-blue-subtle: #eff6ff;

  --accent-purple: #7e22ce;
  --accent-cyan: #0e7490;
  --accent-orange: #c2410c;
  --accent-emerald: #047857;

  --success: #15803d;
  --success-bg: #f0fdf4;
  --success-border: #bbf7d0;

  --warning: #b45309;
  --warning-bg: #fffbeb;
  --warning-border: #fef08a;

  --danger: #b91c1c;
  --danger-bg: #fef2f2;
  --danger-border: #fecaca;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-full: 9999px;

  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);

  --transition: 0.18s ease-in-out;
}

[data-theme="dark"] {
  --bg-page: #0b1120;
  --bg-card: #1e293b;
  --bg-card-subtle: #172033;
  --bg-card-alt: #0f172a;
  --border-color: #334155;
  --border-color-subtle: #1e293b;

  --text-primary: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;
  --text-inverse: #0f172a;

  --brand-blue: #3b82f6;
  --brand-blue-hover: #60a5fa;
  --brand-blue-subtle: #1e3a8a33;

  --accent-purple: #c084fc;
  --accent-cyan: #22d3ee;
  --accent-orange: #fb923c;
  --accent-emerald: #34d399;

  --success: #22c55e;
  --success-bg: #052e1633;
  --success-border: #166534;

  --warning: #f59e0b;
  --warning-bg: #451a0333;
  --warning-border: #854d0e;

  --danger: #ef4444;
  --danger-bg: #450a0a33;
  --danger-border: #991b1b;
}

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

body {
  font-family: var(--font-sans);
  background-color: var(--bg-page);
  color: var(--text-primary);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  padding-bottom: 3rem;
}

/* Focus Management (Accessibility) */
:focus-visible {
  outline: 2px solid var(--brand-blue);
  outline-offset: 2px;
}

/* Main Container */
.app-container {
  max-width: 1040px;
  margin: 0 auto;
  padding: 1.5rem 1rem;
}

/* Header */
.app-header {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
}

.header-title-group {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.header-badge {
  background: var(--brand-blue);
  color: white;
  font-weight: 700;
  font-size: 0.85rem;
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius-sm);
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.app-title {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--text-primary);
  line-height: 1.2;
}

.app-subtitle {
  font-size: 0.9rem;
  color: var(--text-muted);
}

.header-controls {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.btn-icon {
  background: var(--bg-card-subtle);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  padding: 0.5rem 0.85rem;
  border-radius: var(--radius-md);
  font-size: 0.9rem;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-weight: 500;
  transition: all var(--transition);
}

.btn-icon:hover {
  background: var(--border-color-subtle);
}

/* ==========================================================================
   Tab Navigation (Accessible WAI-ARIA with Underline Indicator)
   ========================================================================== */
.tab-container {
  margin-bottom: 1.5rem;
}

.tab-list {
  display: flex;
  border-bottom: 2px solid var(--border-color-subtle);
  gap: 0.5rem;
  overflow-x: auto;
  scrollbar-width: thin;
}

.tab-btn {
  background: transparent;
  border: none;
  font-family: inherit;
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text-muted);
  padding: 0.85rem 1.4rem;
  cursor: pointer;
  position: relative;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  white-space: nowrap;
  transition: color var(--transition);
}

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

/* Border pseudo-element underline (Guidance compliant, forced-colors safe) */
.tab-btn[aria-selected="true"] {
  color: var(--brand-blue);
}

.tab-btn[aria-selected="true"]::after {
  content: "";
  position: absolute;
  inset: auto 0 -2px 0;
  border-bottom: 3px solid var(--brand-blue);
}

.tab-panel {
  display: block;
}

.tab-panel[hidden] {
  display: none;
}

/* ==========================================================================
   Modul 1: Regel-Navigator
   ========================================================================== */
.module-header {
  margin-bottom: 1.25rem;
}

.module-header h2 {
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--text-primary);
}

.module-header p {
  color: var(--text-secondary);
  font-size: 0.95rem;
}

/* Step Bar / Rule Pills */
.rule-stepper {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(130px, 1fr));
  gap: 0.5rem;
  margin-bottom: 1.5rem;
}

.rule-step-btn {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 0.65rem 0.5rem;
  font-family: inherit;
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-secondary);
  cursor: pointer;
  text-align: center;
  transition: all var(--transition);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.2rem;
}

.rule-step-btn:hover {
  border-color: var(--brand-blue);
  color: var(--brand-blue);
}

.rule-step-btn.active {
  background: var(--brand-blue-subtle);
  border-color: var(--brand-blue);
  color: var(--brand-blue);
  box-shadow: var(--shadow-sm);
}

.step-num {
  font-size: 0.72rem;
  text-transform: uppercase;
  color: var(--text-muted);
  font-weight: 700;
}

.rule-step-btn.active .step-num {
  color: var(--brand-blue);
}

/* Rule Detail Card */
.rule-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  box-shadow: var(--shadow-md);
  margin-bottom: 1.5rem;
}

.rule-card-header {
  display: flex;
  align-items: baseline;
  gap: 0.75rem;
  margin-bottom: 1rem;
  border-bottom: 1px solid var(--border-color-subtle);
  padding-bottom: 0.75rem;
}

.rule-badge {
  background: var(--brand-blue);
  color: white;
  font-size: 0.8rem;
  font-weight: 700;
  padding: 0.25rem 0.6rem;
  border-radius: var(--radius-sm);
}

.rule-title {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--text-primary);
}

.rule-explanation {
  font-size: 1.05rem;
  color: var(--text-primary);
  line-height: 1.6;
  margin-bottom: 1.5rem;
}

.rule-explanation strong {
  color: var(--brand-blue);
}

/* Examples Grid */
.examples-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.25rem;
}

@media (min-width: 768px) {
  .examples-grid {
    grid-template-columns: 1fr 1fr;
  }
}

.example-box {
  background: var(--bg-card-subtle);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.25rem;
}

.example-box-header {
  font-size: 0.82rem;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-bottom: 0.6rem;
  display: flex;
  justify-content: space-between;
}

.formula-display {
  font-family: var(--font-mono);
  font-size: 1.3rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  padding: 0.4rem 0.6rem;
  background: var(--bg-card);
  border: 1px solid var(--border-color-subtle);
  border-radius: var(--radius-sm);
  display: inline-block;
}

.name-display {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 0.75rem;
}

.breakdown-list {
  list-style: none;
  font-size: 0.88rem;
  color: var(--text-secondary);
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.breakdown-list li {
  position: relative;
  padding-left: 1.2rem;
}

.breakdown-list li::before {
  content: "•";
  position: absolute;
  left: 0.25rem;
  color: var(--brand-blue);
  font-weight: bold;
}

/* Pitfall / Warning Box */
.pitfall-box {
  margin-top: 1.25rem;
  background: var(--warning-bg);
  border: 1px solid var(--warning-border);
  border-left: 4px solid var(--warning);
  border-radius: var(--radius-md);
  padding: 1rem 1.25rem;
  font-size: 0.92rem;
  color: var(--text-primary);
}

.pitfall-box strong {
  color: var(--warning);
}

/* Nav Buttons inside Modul 1 */
.rule-nav-buttons {
  display: flex;
  justify-content: space-between;
  margin-top: 1.5rem;
}

/* ==========================================================================
   Modul 2: Interaktive Übungen
   ========================================================================== */
.practice-toolbar {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1rem 1.25rem;
  margin-bottom: 1.5rem;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
}

.level-toggle-group {
  display: inline-flex;
  background: var(--bg-card-subtle);
  border: 1px solid var(--border-color);
  padding: 3px;
  border-radius: var(--radius-md);
}

.level-btn {
  background: transparent;
  border: none;
  font-family: inherit;
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--text-secondary);
  padding: 0.45rem 1rem;
  border-radius: calc(var(--radius-md) - 3px);
  cursor: pointer;
  transition: all var(--transition);
}

.level-btn.active {
  background: var(--brand-blue);
  color: white;
  box-shadow: var(--shadow-sm);
}

.practice-stats {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  font-size: 0.9rem;
  font-weight: 600;
}

.stat-item {
  display: flex;
  align-items: center;
  gap: 0.35rem;
}

.stat-badge {
  background: var(--bg-card-subtle);
  border: 1px solid var(--border-color);
  padding: 0.2rem 0.5rem;
  border-radius: var(--radius-sm);
  color: var(--brand-blue);
  font-weight: 700;
}

/* Exercise Card */
.exercise-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 2rem;
  box-shadow: var(--shadow-md);
  margin-bottom: 1.5rem;
}

.exercise-progress-bar-wrap {
  width: 100%;
  height: 6px;
  background: var(--bg-card-subtle);
  border-radius: var(--radius-full);
  margin-bottom: 1.5rem;
  overflow: hidden;
}

.exercise-progress-bar {
  height: 100%;
  background: var(--brand-blue);
  width: 0%;
  transition: width 0.3s ease;
}

.exercise-header {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  margin-bottom: 1rem;
}

.exercise-level-tag {
  font-size: 0.8rem;
  font-weight: 700;
  text-transform: uppercase;
  padding: 0.25rem 0.6rem;
  border-radius: var(--radius-sm);
  background: var(--brand-blue-subtle);
  color: var(--brand-blue);
}

.exercise-counter {
  font-size: 0.88rem;
  color: var(--text-muted);
  font-weight: 600;
}

/* Big Formula/Question Prompt */
.question-prompt {
  text-align: center;
  padding: 1.5rem 1rem;
  margin-bottom: 1.5rem;
  background: var(--bg-card-subtle);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
}

.question-label {
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.target-formula {
  font-family: var(--font-mono);
  font-size: 2rem;
  font-weight: 800;
  color: var(--text-primary);
  display: inline-block;
  letter-spacing: 0.02em;
}

/* ==========================================================================
   Tipp-Kästchen (Details & Summary Accessibility Compliant)
   ========================================================================== */
.hint-details {
  background: var(--bg-card-alt);
  border: 1px solid var(--border-color);
  border-left: 4px solid var(--brand-blue);
  border-radius: var(--radius-md);
  margin-bottom: 1.5rem;
  overflow: hidden;
  transition: all var(--transition);
}

.hint-summary {
  padding: 0.75rem 1rem;
  cursor: pointer;
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--brand-blue);
  list-style: none;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  user-select: none;
}

.hint-summary::-webkit-details-marker {
  display: none;
}

.hint-summary::after {
  content: "▼";
  margin-left: auto;
  font-size: 0.75rem;
  transition: transform 0.2s ease;
}

.hint-details[open] .hint-summary::after {
  transform: rotate(-180deg);
}

.hint-summary:hover {
  background: var(--brand-blue-subtle);
}

.hint-body {
  padding: 0.85rem 1.25rem 1.15rem;
  border-top: 1px solid var(--border-color-subtle);
  font-size: 0.92rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.hint-body strong {
  color: var(--text-primary);
}

/* ==========================================================================
   Exercise Inputs & Interactive Building Blocks
   ========================================================================== */
.input-mode-switcher {
  display: flex;
  justify-content: flex-end;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
}

.input-mode-btn {
  background: transparent;
  border: none;
  font-family: inherit;
  font-size: 0.8rem;
  color: var(--text-muted);
  cursor: pointer;
  text-decoration: underline;
  padding: 0.2rem 0.5rem;
}

.input-mode-btn.active {
  color: var(--brand-blue);
  font-weight: 700;
  text-decoration: none;
}

/* Mode A: Free Text Input */
.text-input-form {
  display: flex;
  gap: 0.75rem;
  margin-bottom: 1.25rem;
}

.input-field {
  flex: 1;
  font-family: inherit;
  font-size: 1.1rem;
  padding: 0.85rem 1.15rem;
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  background: var(--bg-card);
  color: var(--text-primary);
  transition: border-color var(--transition);
}

.input-field:focus {
  border-color: var(--brand-blue);
}

/* Mode B: Bausteine / Word Building Blocks */
.blocks-workspace {
  background: var(--bg-card-subtle);
  border: 2px dashed var(--border-color);
  border-radius: var(--radius-md);
  min-height: 60px;
  padding: 0.75rem;
  margin-bottom: 1rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  align-items: center;
}

.blocks-workspace.empty::after {
  content: "Klicke auf die Bausteine unten, um den Namen zusammenzusetzen...";
  color: var(--text-muted);
  font-size: 0.9rem;
  font-style: italic;
  width: 100%;
  text-align: center;
}

.block-chip {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  padding: 0.45rem 0.85rem;
  border-radius: var(--radius-sm);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  box-shadow: var(--shadow-sm);
  transition: all var(--transition);
  user-select: none;
}

.block-chip:hover {
  transform: translateY(-1px);
  border-color: var(--brand-blue);
}

.block-chip.used {
  opacity: 0.35;
  pointer-events: none;
}

.block-chip.in-workspace {
  background: var(--brand-blue);
  color: white;
  border-color: var(--brand-blue);
}

.block-chip.in-workspace:hover {
  background: var(--danger);
  border-color: var(--danger);
}

.blocks-selection-pool {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-bottom: 1.25rem;
}

/* Action Buttons */
.action-buttons-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  align-items: center;
}

.btn-primary {
  background: var(--brand-blue);
  color: white;
  border: none;
  font-family: inherit;
  font-size: 1rem;
  font-weight: 600;
  padding: 0.85rem 1.6rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  box-shadow: var(--shadow-sm);
  transition: all var(--transition);
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

.btn-primary:hover {
  background: var(--brand-blue-hover);
  box-shadow: var(--shadow-md);
}

.btn-secondary {
  background: var(--bg-card-subtle);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 600;
  padding: 0.85rem 1.3rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition);
}

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

/* Feedback Box */
.feedback-box {
  margin-top: 1.25rem;
  padding: 1.15rem 1.35rem;
  border-radius: var(--radius-md);
  font-size: 0.95rem;
  line-height: 1.5;
  display: none;
  animation: fadeIn 0.25s ease;
}

.feedback-box.correct {
  display: block;
  background: var(--success-bg);
  border: 1px solid var(--success-border);
  color: var(--success);
}

.feedback-box.almost {
  display: block;
  background: var(--warning-bg);
  border: 1px solid var(--warning-border);
  color: var(--warning);
}

.feedback-box.incorrect {
  display: block;
  background: var(--danger-bg);
  border: 1px solid var(--danger-border);
  color: var(--danger);
}

.feedback-title {
  font-weight: 700;
  margin-bottom: 0.35rem;
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

.feedback-details {
  color: var(--text-primary);
  font-size: 0.9rem;
}

/* ==========================================================================
   Quick Reference Modal / Spickzettel
   ========================================================================== */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
  z-index: 1000;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s ease;
}

.modal-overlay.open {
  opacity: 1;
  pointer-events: auto;
}

.modal-content {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  max-width: 750px;
  width: 100%;
  max-height: 85vh;
  overflow-y: auto;
  padding: 1.75rem;
  box-shadow: var(--shadow-lg);
  position: relative;
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.25rem;
  border-bottom: 1px solid var(--border-color-subtle);
  padding-bottom: 0.75rem;
}

.modal-title {
  font-size: 1.25rem;
  font-weight: 700;
}

.close-modal-btn {
  background: transparent;
  border: none;
  font-size: 1.5rem;
  line-height: 1;
  color: var(--text-muted);
  cursor: pointer;
}

.ref-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.88rem;
  margin-bottom: 1.25rem;
}

.ref-table th, .ref-table td {
  border: 1px solid var(--border-color);
  padding: 0.5rem 0.75rem;
  text-align: left;
}

.ref-table th {
  background: var(--bg-card-subtle);
  font-weight: 700;
}

/* Animation */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(-4px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Utility color spans for formula/name breakdowns */
.col-metal   { color: #2563eb; font-weight: 700; }
.col-ligand  { color: #d97706; font-weight: 700; }
.col-prefix  { color: #7c3aed; font-weight: 700; }
.col-charge  { color: #16a34a; font-weight: 700; }
.col-anion   { color: #dc2626; font-weight: 700; }

[data-theme="dark"] .col-metal   { color: #60a5fa; }
[data-theme="dark"] .col-ligand  { color: #fbbf24; }
[data-theme="dark"] .col-prefix  { color: #c084fc; }
[data-theme="dark"] .col-charge  { color: #4ade80; }
[data-theme="dark"] .col-anion   { color: #f87171; }

.set-toggle-group {
  display: inline-flex;
  background: var(--bg-card-subtle);
  border: 1px solid var(--border-color);
  padding: 3px;
  border-radius: var(--radius-md);
}

.set-btn {
  background: transparent;
  border: none;
  font-family: inherit;
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-secondary);
  padding: 0.4rem 0.8rem;
  border-radius: calc(var(--radius-md) - 3px);
  cursor: pointer;
  transition: all var(--transition);
}

.set-btn.active {
  background: var(--brand-blue);
  color: white;
  box-shadow: var(--shadow-sm);
}