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

:root {
  --primary: #2563eb;
  --primary-dark: #1e40af;
  --success: #10b981;
  --danger: #ef4444;
  --warning: #f59e0b;
  --gray-50: #f9fafb;
  --gray-100: #f3f4f6;
  --gray-200: #e5e7eb;
  --gray-300: #d1d5db;
  --gray-600: #4b5563;
  --gray-700: #374151;
  --gray-900: #111827;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  min-height: 100vh;
  color: var(--gray-900);
}

.container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 20px;
}

/* Navbar */
.navbar {
  background: white;
  padding: 20px 30px;
  border-radius: 15px;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 30px;
}

.nav-brand h1 {
  font-size: 24px;
  color: var(--primary);
}

.nav-links {
  display: flex;
  gap: 20px;
}

.nav-link {
  text-decoration: none;
  color: var(--gray-600);
  font-weight: 500;
  padding: 8px 16px;
  border-radius: 8px;
  transition: all 0.3s;
}

.nav-link:hover {
  background: var(--gray-100);
  color: var(--primary);
}

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

/* Content */
.content {
  background: white;
  border-radius: 15px;
  padding: 30px;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

/* Header */
.header {
  margin-bottom: 30px;
}

.header h2 {
  margin-bottom: 20px;
  font-size: 28px;
}

.stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 20px;
}

.stat-card {
  background: var(--gray-50);
  padding: 20px;
  border-radius: 10px;
  border-left: 4px solid var(--primary);
}

.stat-card.paid {
  border-left-color: var(--success);
}

.stat-card.unpaid {
  border-left-color: var(--danger);
}

.stat-card.revenue {
  border-left-color: #8b5cf6;
  background: linear-gradient(135deg, #faf5ff 0%, #f3e8ff 100%);
}

.stat-card.revenue-month {
  border-left-color: #0891b2;
  background: linear-gradient(135deg, #ecfeff 0%, #cffafe 100%);
}

.stat-label {
  display: block;
  color: var(--gray-600);
  font-size: 14px;
  margin-bottom: 8px;
}

.stat-value {
  display: block;
  font-size: 32px;
  font-weight: 700;
  color: var(--gray-900);
}

/* Table */
.clients-table {
  overflow-x: auto;
  margin-top: 20px;
}

table {
  width: 100%;
  border-collapse: collapse;
}

thead {
  background: var(--gray-50);
}

th {
  padding: 15px;
  text-align: left;
  font-weight: 600;
  color: var(--gray-700);
  border-bottom: 2px solid var(--gray-200);
}

td {
  padding: 15px;
  border-bottom: 1px solid var(--gray-200);
}

tr:hover {
  background: var(--gray-50);
}

.expired-row {
  background: #fef2f2;
}

.warning-row {
  background: #fffbeb;
}

.client-name {
  font-weight: 600;
  color: var(--gray-900);
}

.account-number {
  font-family: 'Courier New', monospace;
  color: var(--primary);
  font-weight: 500;
}

.price {
  font-weight: 600;
  color: var(--gray-700);
}

/* Badges */
.badge {
  padding: 6px 12px;
  border-radius: 20px;
  font-size: 13px;
  font-weight: 600;
  display: inline-block;
}

.badge-paid {
  background: #d1fae5;
  color: #065f46;
}

.badge-unpaid {
  background: #fee2e2;
  color: #991b1b;
}

.days-left {
  padding: 4px 10px;
  border-radius: 15px;
  font-size: 13px;
  font-weight: 500;
}

.days-left.active {
  background: #d1fae5;
  color: #065f46;
}

.days-left.warning {
  background: #fef3c7;
  color: #92400e;
}

.days-left.expired {
  background: #fee2e2;
  color: #991b1b;
}

/* Buttons */
.btn-edit {
  background: var(--primary);
  color: white;
  border: none;
  padding: 8px 16px;
  border-radius: 6px;
  cursor: pointer;
  font-weight: 500;
  transition: all 0.3s;
  margin-right: 8px;
}

.btn-edit:hover {
  background: var(--primary-dark);
  transform: translateY(-2px);
}

.btn-delete {
  background: var(--danger);
  color: white;
  border: none;
  padding: 8px 16px;
  border-radius: 6px;
  cursor: pointer;
  font-weight: 500;
  transition: all 0.3s;
}

.btn-delete:hover {
  background: #dc2626;
  transform: translateY(-2px);
}

.btn-primary {
  background: var(--primary);
  color: white;
  border: none;
  padding: 12px 24px;
  border-radius: 8px;
  cursor: pointer;
  font-weight: 600;
  font-size: 16px;
  transition: all 0.3s;
}

.btn-primary:hover {
  background: var(--primary-dark);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}

.btn-primary:disabled {
  background: var(--gray-300);
  cursor: not-allowed;
  transform: none;
}

.btn-secondary {
  background: white;
  color: var(--gray-700);
  border: 2px solid var(--gray-300);
  padding: 12px 24px;
  border-radius: 8px;
  cursor: pointer;
  font-weight: 600;
  font-size: 16px;
  transition: all 0.3s;
}

.btn-secondary:hover {
  background: var(--gray-50);
  border-color: var(--gray-400);
}

/* Forms */
.form-container {
  max-width: 600px;
  margin: 0 auto;
}

.form-container h2 {
  margin-bottom: 10px;
  font-size: 28px;
}

.subtitle {
  color: var(--gray-600);
  margin-bottom: 30px;
}

.form-group {
  margin-bottom: 20px;
}

.form-group label {
  display: block;
  margin-bottom: 8px;
  font-weight: 600;
  color: var(--gray-700);
}

.help-text {
  font-weight: 400;
  color: var(--gray-500);
  font-size: 13px;
}

.form-group input,
.form-group textarea {
  width: 100%;
  padding: 12px;
  border: 2px solid var(--gray-300);
  border-radius: 8px;
  font-size: 16px;
  font-family: inherit;
  transition: all 0.3s;
}

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

.form-actions {
  display: flex;
  gap: 15px;
  margin-top: 30px;
}

.form-actions button {
  flex: 1;
}

/* Messages */
.message {
  padding: 15px;
  border-radius: 8px;
  margin-top: 20px;
  font-weight: 500;
}

.message.success {
  background: #d1fae5;
  color: #065f46;
  border: 1px solid #10b981;
}

.message.error {
  background: #fee2e2;
  color: #991b1b;
  border: 1px solid #ef4444;
}

.no-data {
  text-align: center;
  padding: 40px !important;
  color: var(--gray-500);
  font-style: italic;
}

/* Messaging specific */
.char-counter {
  text-align: right;
  font-size: 14px;
  color: var(--gray-600);
  margin-top: 5px;
}

.message-preview {
  background: var(--gray-50);
  padding: 20px;
  border-radius: 10px;
  margin: 20px 0;
}

.message-preview h3 {
  margin-bottom: 10px;
  font-size: 16px;
  color: var(--gray-700);
}

.preview-box {
  background: white;
  padding: 15px;
  border-radius: 8px;
  border: 2px dashed var(--gray-300);
  min-height: 80px;
  color: var(--gray-600);
  font-style: italic;
}

/* Modal Styles */
.modal {
  display: none;
  position: fixed;
  z-index: 1000;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  overflow: auto;
  background-color: rgba(0, 0, 0, 0.5);
  animation: fadeIn 0.3s;
}

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

.modal-content {
  background-color: white;
  margin: 5% auto;
  padding: 0;
  border-radius: 15px;
  width: 90%;
  max-width: 600px;
  box-shadow: 0 10px 40px rgba(0, 0, 0, 0.2);
  animation: slideDown 0.3s;
}

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

.modal-header {
  padding: 25px 30px;
  border-bottom: 2px solid var(--gray-200);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.modal-header h2 {
  margin: 0;
  font-size: 24px;
  color: var(--gray-900);
}

.close {
  color: var(--gray-500);
  font-size: 32px;
  font-weight: bold;
  cursor: pointer;
  transition: color 0.3s;
  line-height: 1;
}

.close:hover {
  color: var(--gray-900);
}

.modal form {
  padding: 30px;
}

.checkbox-group {
  background: var(--gray-50);
  padding: 15px;
  border-radius: 8px;
  border: 2px solid var(--gray-200);
}

.checkbox-label {
  display: flex;
  align-items: center;
  gap: 10px;
  cursor: pointer;
  font-weight: 600;
  color: var(--gray-700);
}

.checkbox-label input[type="checkbox"] {
  width: 20px;
  height: 20px;
  cursor: pointer;
  accent-color: var(--primary);
}

.checkbox-label span {
  user-select: none;
}

.btn-loading {
  display: inline-flex;
  align-items: center;
  gap: 8px;
}

/* Responsive */
@media (max-width: 768px) {
  .navbar {
    flex-direction: column;
    gap: 20px;
  }
  

  .nav-links {
    width: 100%;
    justify-content: center;
  }

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

  table {
    font-size: 14px;
  }

  th, td {
    padding: 10px;
  }

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