/* ===== CSS VARIABLES ===== */
:root {
  --primary-color: #3498db;
  --primary-dark: #2980b9;
  --success-color: #27ae60;
  --success-dark: #229954;
  --danger-color: #e74c3c;
  --danger-dark: #c0392b;
  --secondary-color: #95a5a6;
  --secondary-dark: #7f8c8d;

  --bg-primary: #f5f7fa;
  --bg-secondary: #ffffff;
  --bg-card: #ffffff;

  --text-primary: #2c3e50;
  --text-secondary: #5a6c7d;
  --text-muted: #95a5a6;

  --border-color: #e1e8ed;
  --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.08);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.15);

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;

  --spacing-xs: 8px;
  --spacing-sm: 12px;
  --spacing-md: 16px;
  --spacing-lg: 24px;
  --spacing-xl: 32px;
}

/* ===== DARK MODE VARIABLES ===== */
body.dark-mode {
  --bg-primary: #1a1d23;
  --bg-secondary: #22272e;
  --bg-card: #2d333b;

  --text-primary: #e6edf3;
  --text-secondary: #adbac7;
  --text-muted: #768390;

  --border-color: #444c56;
  --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.5);
}

/* ===== RESET & BASE ===== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  padding-top: 80px;
  transition: background 0.3s ease, color 0.3s ease;
}

/* ===== TOAST NOTIFICATIONS ===== */
#toast-container {
  position: fixed;
  top: 90px;
  right: 20px;
  z-index: 10000;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.toast {
  background: var(--bg-card);
  color: var(--text-primary);
  padding: 16px 20px;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  min-width: 280px;
  max-width: 400px;
  transform: translateX(450px);
  transition: transform 0.3s ease;
  border-left: 4px solid var(--primary-color);
}

.toast.show {
  transform: translateX(0);
}

.toast.toast-success {
  border-left-color: var(--success-color);
}

.toast.toast-error {
  border-left-color: var(--danger-color);
}

.toast.toast-warning {
  border-left-color: #f39c12;
}

/* ===== LOADING OVERLAY ===== */
.loading-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.6);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 9999;
  transition: opacity 0.3s ease;
}

.spinner {
  width: 50px;
  height: 50px;
  border: 4px solid rgba(255, 255, 255, 0.3);
  border-top: 4px solid var(--primary-color);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

/* ===== MODAL ===== */
.modal {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.6);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 9998;
  padding: 20px;
}

.modal-content {
  background: var(--bg-card);
  padding: var(--spacing-xl);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  max-width: 500px;
  width: 100%;
  animation: modalSlideIn 0.3s ease;
}

@keyframes modalSlideIn {
  from {
    transform: translateY(-50px);
    opacity: 0;
  }
  to {
    transform: translateY(0);
    opacity: 1;
  }
}

.modal-content h3 {
  margin-bottom: var(--spacing-md);
  color: var(--text-primary);
  font-size: 1.5rem;
}

.modal-content p {
  margin-bottom: var(--spacing-lg);
  color: var(--text-secondary);
}

.modal-actions {
  display: flex;
  gap: var(--spacing-sm);
  justify-content: flex-end;
}

/* ===== FIXED HEADER ===== */
.fixed-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  background: var(--primary-color);
  color: white;
  padding: var(--spacing-md) var(--spacing-lg);
  box-shadow: var(--shadow-md);
  z-index: 1000;
  transition: background 0.3s ease;
}

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

.fixed-header h1 {
  font-size: 1.5rem;
  font-weight: 600;
  margin: 0;
}

.icon-btn {
  background: rgba(255, 255, 255, 0.2);
  border: none;
  padding: 8px 12px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: background 0.3s ease;
  font-size: 1.2rem;
}

.icon-btn:hover {
  background: rgba(255, 255, 255, 0.3);
}

/* ===== CONTAINER ===== */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: var(--spacing-lg);
}

/* ===== ANALYTICS DASHBOARD ===== */
.analytics-dashboard {
  margin-bottom: var(--spacing-xl);
}

.analytics-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-md);
}

.analytics-card {
  background: var(--bg-card);
  padding: var(--spacing-lg);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.analytics-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.analytics-icon {
  font-size: 2.5rem;
}

.analytics-info {
  flex: 1;
}

.analytics-value {
  font-size: 1.8rem;
  font-weight: 700;
  color: var(--text-primary);
}

.analytics-label {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-top: 4px;
}

/* ===== SECTION HEADER ===== */
.section-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--spacing-lg);
  flex-wrap: wrap;
  gap: var(--spacing-md);
}

.section-header h2 {
  font-size: 1.8rem;
  color: var(--text-primary);
}

.action-buttons {
  display: flex;
  gap: var(--spacing-sm);
}

/* ===== SEARCH & FILTER ===== */
.search-filter-bar {
  margin-bottom: var(--spacing-lg);
}

.search-input {
  width: 100%;
  padding: var(--spacing-sm) var(--spacing-md);
  font-size: 1rem;
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  background: var(--bg-card);
  color: var(--text-primary);
  transition: border-color 0.3s ease, box-shadow 0.3s ease;
}

.search-input:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.1);
}

/* ===== CARDS ===== */
.card {
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

/* ===== FORMS ===== */
.form-card {
  padding: var(--spacing-lg);
  margin-bottom: var(--spacing-lg);
}

.form-card h3 {
  margin-bottom: var(--spacing-md);
  color: var(--text-primary);
  font-size: 1.2rem;
}

.form-group {
  display: flex;
  gap: var(--spacing-sm);
  flex-wrap: wrap;
}

.form-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-sm);
}

.form-input {
  flex: 1;
  padding: var(--spacing-sm) var(--spacing-md);
  font-size: 1rem;
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  background: var(--bg-secondary);
  color: var(--text-primary);
  transition: border-color 0.3s ease, box-shadow 0.3s ease;
  min-width: 0;
}

.form-input:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.1);
}

.form-input.compact {
  flex: none;
  width: auto;
  min-width: 180px;
}

.form-error {
  color: var(--danger-color);
  font-size: 0.9rem;
  margin-top: var(--spacing-sm);
}

/* ===== BUTTONS ===== */
.btn {
  padding: var(--spacing-sm) var(--spacing-lg);
  font-size: 1rem;
  font-weight: 600;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: background 0.3s ease, transform 0.1s ease;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  white-space: nowrap;
}

.btn:hover {
  transform: translateY(-1px);
}

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

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

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

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

.btn-success:hover {
  background: var(--success-dark);
}

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

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

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

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

.btn-sm {
  padding: 8px 16px;
  font-size: 0.9rem;
}

.back-btn {
  margin-bottom: var(--spacing-lg);
}

/* ===== PERSON CARDS ===== */
.persons-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--spacing-md);
}

.person-card {
  padding: var(--spacing-lg);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.person-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.person-info {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: var(--spacing-md);
}

.person-name {
  font-size: 1.3rem;
  color: var(--text-primary);
  margin: 0;
}

.person-balance {
  font-size: 1.5rem;
  font-weight: 700;
}

.person-balance.positive {
  color: var(--success-color);
}

.person-balance.negative {
  color: var(--danger-color);
}

.person-actions {
  display: flex;
  gap: var(--spacing-sm);
  flex-wrap: wrap;
}

/* ===== TRANSACTION VIEW ===== */
.transaction-header {
  text-align: center;
  margin-bottom: var(--spacing-xl);
}

.transaction-header h2 {
  font-size: 1.8rem;
  color: var(--text-primary);
  margin-bottom: var(--spacing-lg);
}

.person-stats {
  display: flex;
  justify-content: center;
  gap: var(--spacing-xl);
  flex-wrap: wrap;
  margin-top: var(--spacing-md);
}

.stat-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: var(--spacing-md);
  background: var(--bg-card);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  min-width: 150px;
}

.stat-label {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-bottom: var(--spacing-xs);
  font-weight: 500;
}

.stat-value {
  font-size: 1.4rem;
  font-weight: 700;
}

.balance-display {
  font-size: 1.3rem;
  color: var(--text-secondary);
}

.balance-amount {
  font-weight: 700;
  font-size: 1.6rem;
}

.balance-amount.positive {
  color: var(--success-color);
}

.balance-amount.negative {
  color: var(--danger-color);
}

/* ===== TRANSACTION CONTROLS ===== */
.transaction-controls {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--spacing-lg);
  gap: var(--spacing-md);
  flex-wrap: wrap;
}

.sort-controls {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.sort-controls label {
  font-weight: 600;
  color: var(--text-secondary);
}

/* ===== TRANSACTION CARDS ===== */
.transactions-container {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.transaction-card {
  padding: var(--spacing-lg);
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  border-left: 4px solid var(--border-color);
}

.transaction-card.payment {
  border-left-color: var(--danger-color);
}

.transaction-card.received {
  border-left-color: var(--success-color);
}

.transaction-icon {
  font-size: 2rem;
  flex-shrink: 0;
}

.transaction-details {
  flex: 1;
  min-width: 0;
}

.transaction-type {
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 4px;
}

.transaction-amount {
  font-size: 1.3rem;
  font-weight: 700;
  margin-bottom: 4px;
}

.transaction-amount.payment {
  color: var(--danger-color);
}

.transaction-amount.received {
  color: var(--success-color);
}

.transaction-description {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-bottom: 4px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.transaction-date {
  color: var(--text-muted);
  font-size: 0.85rem;
}

/* ===== EMPTY STATE ===== */
.empty-state {
  text-align: center;
  padding: var(--spacing-xl);
  color: var(--text-muted);
  font-size: 1.1rem;
}

/* ===== UTILITY ===== */
.hidden {
  display: none !important;
}

.icon {
  display: inline-block;
}

/* ===== RESPONSIVE - TABLET ===== */
@media (max-width: 768px) {
  body {
    padding-top: 70px;
  }

  .container {
    padding: var(--spacing-md);
  }

  .fixed-header {
    padding: var(--spacing-sm) var(--spacing-md);
  }

  .fixed-header h1 {
    font-size: 1.3rem;
  }

  #toast-container {
    right: 10px;
    top: 80px;
  }

  .toast {
    min-width: 260px;
  }

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

  .analytics-card {
    padding: var(--spacing-md);
  }

  .analytics-icon {
    font-size: 2rem;
  }

  .analytics-value {
    font-size: 1.5rem;
  }

  .section-header h2 {
    font-size: 1.5rem;
  }

  .persons-grid {
    grid-template-columns: 1fr;
  }

  .form-grid {
    grid-template-columns: 1fr;
  }

  .transaction-controls {
    flex-direction: column;
    align-items: stretch;
  }

  .sort-controls {
    width: 100%;
  }

  .sort-controls .form-input {
    flex: 1;
  }

  .person-stats {
    gap: var(--spacing-md);
  }

  .stat-item {
    min-width: 130px;
    padding: var(--spacing-sm);
  }

  .stat-value {
    font-size: 1.2rem;
  }
}

/* ===== RESPONSIVE - MOBILE ===== */
@media (max-width: 480px) {
  body {
    padding-top: 65px;
  }

  .container {
    padding: var(--spacing-sm);
  }

  .fixed-header {
    padding: 10px var(--spacing-sm);
  }

  .fixed-header h1 {
    font-size: 1.1rem;
  }

  .icon-btn {
    padding: 6px 10px;
    font-size: 1rem;
  }

  #toast-container {
    left: 10px;
    right: 10px;
    top: 75px;
  }

  .toast {
    min-width: auto;
    max-width: none;
  }

  .analytics-grid {
    grid-template-columns: 1fr;
    gap: var(--spacing-sm);
  }

  .analytics-card {
    padding: var(--spacing-sm);
  }

  .analytics-icon {
    font-size: 1.8rem;
  }

  .analytics-value {
    font-size: 1.3rem;
  }

  .analytics-label {
    font-size: 0.85rem;
  }

  .section-header {
    flex-direction: column;
    align-items: stretch;
  }

  .section-header h2 {
    font-size: 1.3rem;
  }

  .action-buttons {
    width: 100%;
  }

  .action-buttons .btn {
    flex: 1;
  }

  .form-group {
    flex-direction: column;
  }

  .form-group .btn {
    width: 100%;
  }

  .person-info {
    flex-direction: column;
    align-items: flex-start;
  }

  .person-name {
    font-size: 1.2rem;
  }

  .person-balance {
    font-size: 1.3rem;
  }

  .person-actions {
    width: 100%;
  }

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

  .transaction-header h2 {
    font-size: 1.5rem;
  }

  .balance-display {
    font-size: 1.1rem;
  }

  .balance-amount {
    font-size: 1.4rem;
  }

  .transaction-card {
    padding: var(--spacing-sm);
    flex-wrap: wrap;
  }

  .transaction-icon {
    font-size: 1.5rem;
  }

  .transaction-amount {
    font-size: 1.2rem;
  }

  .transaction-card .btn {
    width: 100%;
    margin-top: var(--spacing-sm);
  }

  .modal-content {
    padding: var(--spacing-lg);
  }

  .modal-actions {
    flex-direction: column;
  }

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

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