:root {
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --primary-light: #3b82f6;
  
  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-card: #ffffff;
  --bg-hover: #f1f5f9;
  
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-tertiary: #64748b;
  
  --border: #e2e8f0;
  --border-light: #cbd5e1;
  
  --success: #10b981;
  --danger: #ef4444;
  --warning: #f59e0b;
  
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow: 0 1px 3px 0 rgb(0 0 0 / 0.1);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
}

[data-theme="dark"] {
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-card: #1e293b;
  --bg-hover: #334155;
  
  --text-primary: #f1f5f9;
  --text-secondary: #cbd5e1;
  --text-tertiary: #94a3b8;
  
  --border: #334155;
  --border-light: #475569;
  
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.3);
  --shadow: 0 1px 3px 0 rgb(0 0 0 / 0.4);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.5);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.6);
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background: var(--bg-secondary);
  color: var(--text-primary);
  line-height: 1.6;
  transition: background-color 0.3s ease, color 0.3s ease;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

/* Header */
header {
  background: var(--bg-primary);
  border-bottom: 1px solid var(--border);
  box-shadow: var(--shadow-sm);
  position: sticky;
  top: 0;
  z-index: 1000;
  transition: background-color 0.3s ease;
}

.header-content {
  max-width: 1200px;
  margin: 0 auto;
  padding: 1.5rem 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

header h1 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: -0.025em;
}

.theme-toggle {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 50%;
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all 0.2s ease;
  font-size: 1.2rem;
}

.theme-toggle:hover {
  background: var(--bg-hover);
  transform: scale(1.05);
}

/* Navigation */
nav {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 2rem 1rem;
  display: flex;
  gap: 0.5rem;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.nav-btn {
  background: transparent;
  border: none;
  padding: 0.625rem 1.25rem;
  border-radius: 0.5rem;
  cursor: pointer;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition: all 0.2s ease;
  white-space: nowrap;
}

.nav-btn:hover {
  background: var(--bg-hover);
  color: var(--text-primary);
}

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

/* Main Content */
main {
  flex: 1;
  max-width: 1200px;
  margin: 0 auto;
  padding: 2rem;
  width: 100%;
}

.view {
  display: none;
}

.view.active {
  display: block;
  animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

h2 {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  color: var(--text-primary);
  letter-spacing: -0.025em;
}

.section-subtitle {
  color: var(--text-tertiary);
  margin-bottom: 2rem;
  font-size: 0.9375rem;
}

h3 {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 1rem;
  color: var(--text-primary);
}

/* Form Styles */
.form-group {
  margin-bottom: 1.5rem;
}

.form-group label {
  display: block;
  margin-bottom: 0.5rem;
  font-weight: 500;
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.tooltip {
  position: relative;
  cursor: help;
  color: var(--primary);
  margin-left: 0.25rem;
}

.tooltip::after {
  content: attr(data-tip);
  position: absolute;
  bottom: 125%;
  left: 50%;
  transform: translateX(-50%);
  padding: 0.5rem 0.75rem;
  background: var(--text-primary);
  color: var(--bg-primary);
  border-radius: 0.375rem;
  font-size: 0.75rem;
  white-space: nowrap;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s;
  z-index: 100;
  box-shadow: var(--shadow-lg);
}

.tooltip:hover::after {
  opacity: 1;
}

.form-group input,
.form-group select {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 1px solid var(--border);
  border-radius: 0.5rem;
  font-size: 1rem;
  background: var(--bg-card);
  color: var(--text-primary);
  transition: all 0.2s ease;
  font-family: inherit;
}

.form-group input::placeholder {
  color: var(--text-tertiary);
}

.form-group input:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form-group input:hover:not(:focus),
.form-group select:hover:not(:focus) {
  border-color: var(--border-light);
}

.error-message {
  display: block;
  color: var(--danger);
  font-size: 0.75rem;
  margin-top: 0.25rem;
  min-height: 1rem;
}

/* Loading */
.loading {
  text-align: center;
  padding: 2rem;
  color: var(--text-tertiary);
}

.loading::after {
  content: "";
  display: inline-block;
  width: 1rem;
  height: 1rem;
  border: 2px solid var(--border);
  border-top-color: var(--primary);
  border-radius: 50%;
  margin-left: 0.5rem;
  animation: spin 0.8s linear infinite;
}

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

/* Kurse Container */
.kurse-container {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}

.kurs-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  padding: 1.5rem;
  cursor: pointer;
  transition: all 0.2s ease;
  box-shadow: var(--shadow-sm);
}

.kurs-card:hover:not(.voll) {
  border-color: var(--primary);
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.kurs-card.selected {
  border-color: var(--primary);
  background: rgba(37, 99, 235, 0.05);
  box-shadow: var(--shadow-md);
}

.kurs-card.voll {
  opacity: 0.5;
  cursor: not-allowed;
}

.kurs-card label {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  cursor: pointer;
  margin-bottom: 0.75rem;
}

.kurs-card input[type="checkbox"] {
  width: 1.25rem;
  height: 1.25rem;
  cursor: pointer;
  accent-color: var(--primary);
}

.kurs-card input[type="checkbox"]:checked {
  animation: checkboxPop 0.2s ease;
}

@keyframes checkboxPop {
  0%, 100% {
    transform: scale(1);
  }
  50% {
    transform: scale(1.15);
  }
}

.kurs-card strong {
  font-size: 1.125rem;
  color: var(--text-primary);
  font-weight: 600;
}

.kurs-info {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

.kurs-info p {
  margin-bottom: 0.5rem;
}

.kurs-info strong {
  font-size: 0.875rem;
  color: var(--text-primary);
  font-weight: 600;
}

/* Buttons */
.actions {
  margin-top: 1.5rem;
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
}

.btn-primary {
  background: var(--primary);
  color: white;
  border: none;
  padding: 0.75rem 1.5rem;
  border-radius: 0.5rem;
  font-size: 1rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s ease;
  box-shadow: var(--shadow-sm);
}

.btn-primary:hover:not(:disabled) {
  background: var(--primary-hover);
  box-shadow: var(--shadow-md);
  transform: translateY(-1px);
}

.btn-primary:active {
  transform: translateY(0);
}

.btn-primary:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.btn-secondary {
  background: transparent;
  color: var(--primary);
  border: 1px solid var(--primary);
  padding: 0.625rem 1.25rem;
  border-radius: 0.5rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s ease;
}

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

.btn-ghost {
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border);
  padding: 0.625rem 1.25rem;
  border-radius: 0.5rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s ease;
}

.btn-ghost:hover {
  background: var(--bg-hover);
  color: var(--text-primary);
}

.btn-loader {
  display: flex;
  align-items: center;
  justify-content: center;
}

.spinner {
  display: inline-block;
  width: 1rem;
  height: 1rem;
  border: 2px solid rgba(255, 255, 255, 0.3);
  border-top-color: white;
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  margin-right: 0.5rem;
}

/* Messages */
.meldung {
  margin-top: 2rem;
  padding: 1rem 1.25rem;
  border-radius: 0.75rem;
  border-left: 4px solid;
  animation: slideIn 0.3s ease;
  box-shadow: var(--shadow-sm);
}

@keyframes slideIn {
  from {
    opacity: 0;
    transform: translateX(-10px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

.meldung h3 {
  margin-bottom: 0.5rem;
  font-size: 1rem;
  font-weight: 600;
}

.meldung p {
  font-size: 0.9375rem;
  line-height: 1.6;
}

.meldung.erfolg {
  background: rgba(16, 185, 129, 0.1);
  border-color: var(--success);
  color: var(--text-primary);
}

.meldung.fehler {
  background: rgba(239, 68, 68, 0.1);
  border-color: var(--danger);
  color: var(--text-primary);
}

.meldungs-actions {
  margin-top: 1rem;
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
}

.hidden {
  display: none !important;
}

/* Tabs */
.tabs {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
  border-bottom: 1px solid var(--border);
  padding-bottom: 0.5rem;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.tab-btn {
  background: transparent;
  border: none;
  padding: 0.625rem 1.25rem;
  cursor: pointer;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  border-radius: 0.5rem;
  transition: all 0.2s ease;
  white-space: nowrap;
}

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

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

.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
  animation: fadeIn 0.2s ease;
}

/* Tables */
.bericht-table {
  width: 100%;
  border-collapse: collapse;
  background: var(--bg-card);
  border-radius: 0.75rem;
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--border);
}

.bericht-table th,
.bericht-table td {
  padding: 1rem;
  text-align: left;
  border-bottom: 1px solid var(--border);
}

.bericht-table thead th {
  background: var(--bg-secondary);
  font-weight: 600;
  font-size: 0.875rem;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.bericht-table tbody tr {
  transition: background 0.15s ease;
}

.bericht-table tbody tr:hover {
  background: var(--bg-hover);
}

.bericht-table tbody tr:last-child td {
  border-bottom: none;
}

.bericht-table td {
  font-size: 0.9375rem;
  color: var(--text-secondary);
}

.bericht-table td strong {
  color: var(--text-primary);
  font-weight: 600;
}

.bericht-table td small {
  color: var(--text-tertiary);
  font-size: 0.8125rem;
}

.detail-liste {
  list-style: none;
  padding: 0;
  margin: 0;
}

.detail-liste li {
  padding: 0.25rem 0;
  font-size: 0.875rem;
}

/* Rechnung */
.rechnung {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  padding: 2rem;
  margin-top: 1.5rem;
  box-shadow: var(--shadow-sm);
}

.rechnung-header {
  display: flex;
  justify-content: space-between;
  margin-bottom: 2rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border);
}

.rechnung-header h3 {
  font-size: 1.5rem;
  margin-bottom: 0.5rem;
  font-weight: 700;
}

.rechnung-header p,
.rechnung p {
  margin: 0.25rem 0;
  color: var(--text-secondary);
  font-size: 0.9375rem;
}

.rechnung h4 {
  font-size: 1.125rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 0.75rem;
}

.rechnung-table {
  width: 100%;
  margin-top: 1.5rem;
  border-collapse: collapse;
  border: 1px solid var(--border);
  border-radius: 0.5rem;
  overflow: hidden;
}

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

.rechnung-table th {
  background: var(--bg-secondary);
  font-weight: 600;
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.rechnung-table tbody tr:last-child td {
  border-bottom: none;
}

.rechnung-table td {
  font-size: 0.9375rem;
  color: var(--text-secondary);
}

.rechnung-summe {
  margin-top: 1.5rem;
  text-align: right;
  border-top: 2px solid var(--border);
  padding-top: 1rem;
  font-variant-numeric: tabular-nums;
}

.rechnung-summe div {
  padding: 0.5rem 0;
  font-size: 1rem;
  color: var(--text-secondary);
}

.rechnung-summe .gesamt {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--primary);
  margin-top: 0.5rem;
}

/* Footer */
footer {
  background: var(--bg-primary);
  border-top: 1px solid var(--border);
  padding: 1.5rem 2rem;
  text-align: center;
  color: var(--text-tertiary);
  font-size: 0.875rem;
  transition: background-color 0.3s ease;
}

/* Inline helpers */
.inline {
  display: flex;
  gap: 0.75rem;
  align-items: center;
}

/* Print styles */
@media print {
  body {
    background: white;
  }
  .container {
    background: white;
  }
  header,
  nav,
  .btn-primary,
  footer {
    display: none;
  }
  main {
    padding: 20px;
    background: white;
  }
  .rechnung {
    border-color: #000;
    background: white;
    color: #000;
  }
  .rechnung * {
    color: #000 !important;
  }
}

/* Responsive */
@media (max-width: 1024px) {
  main {
    padding: 1.5rem;
  }
  .header-content,
  nav {
    padding-left: 1.5rem;
    padding-right: 1.5rem;
  }
}

@media (max-width: 768px) {
  main {
    padding: 1rem;
  }
  
  .header-content,
  nav {
    padding-left: 1rem;
    padding-right: 1rem;
  }
  
  h2 {
    font-size: 1.5rem;
  }
  
  .nav-btn {
    padding: 0.5rem 1rem;
    font-size: 0.8125rem;
  }
  
  .kurse-container {
    grid-template-columns: 1fr;
  }
  
  .rechnung {
    padding: 1.5rem 1rem;
  }
  
  .rechnung-header {
    flex-direction: column;
    gap: 1rem;
  }
  
  .meldungs-actions {
    flex-direction: column;
  }
  
  .inline {
    flex-direction: column;
    align-items: stretch;
  }
  
  .bericht-table th,
  .bericht-table td {
    padding: 0.75rem 0.5rem;
    font-size: 0.875rem;
  }
  
  .form-group input,
  .form-group select {
    font-size: 16px; /* prevents iOS zoom */
  }
}

/* Accessibility */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

*:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}