/* --- Modern CSS Variables --- */
:root {
    --primary: #2bb9bf;
    --primary-dark: #20a7ad;
    --primary-light: #e9fafb;
    --accent: #ffd85a;
    --accent-dark: #f5c931;
    --bg: #faf7f0;
    --bg-gradient: linear-gradient(135deg, #faf7f0 0%, #f0f7fa 100%);
    --text: #1a1a1a;
    --text-light: #6b7280;
    --card: #ffffff;
    --card-shadow: 0 10px 40px rgba(0, 0, 0, 0.08);
    --card-shadow-hover: 0 15px 50px rgba(0, 0, 0, 0.12);
    --border: #e5e7eb;
    --success: #10b981;
    --warning: #f59e0b;
    --danger: #ef4444;
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  }
  
  /* --- Base Styles --- */
  * {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
  }
  
  html {
    scroll-behavior: smooth;
  }
  
  body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    color: var(--text);
    background: var(--bg-gradient);
    line-height: 1.6;
    min-height: 100vh;
  }
  
  .container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 30px 20px;
  }
  
  /* --- Header & Navigation --- */
  .header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 30px;
  }
  
  .logo {
    display: flex;
    align-items: center;
    gap: 12px;
    text-decoration: none;
    color: var(--text);
    font-weight: 700;
    font-size: 1.25rem;
  }
  
  .logo-img {
    height: 40px;
    width: auto;
  }
  
  .back-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 18px;
    background: white;
    color: var(--text);
    text-decoration: none;
    border-radius: var(--radius-md);
    font-weight: 600;
    transition: var(--transition);
    border: 1px solid var(--border);
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.05);
  }
  
  .back-btn:hover {
    background: #f9fafb;
    transform: translateX(-3px);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.08);
  }
  
  .back-btn i {
    font-size: 0.9rem;
  }
  
  /* --- Hero Section --- */
  .hero {
    background: linear-gradient(135deg, rgba(43, 185, 191, 0.1) 0%, rgba(255, 216, 90, 0.1) 100%),
                url('https://images.unsplash.com/photo-1495197359483-d092478c170a?q=80&w=1600&auto=format&fit=crop') center/cover no-repeat;
    padding: 60px 30px;
    text-align: center;
    border-radius: var(--radius-xl);
    margin-bottom: 40px;
    position: relative;
    overflow: hidden;
  }
  
  .hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(255, 255, 255, 0.85);
    z-index: 1;
  }
  
  .hero-content {
    position: relative;
    z-index: 2;
  }
  
  .hero h1 {
    font-size: 2.5rem;
    font-weight: 800;
    margin-bottom: 15px;
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
  }
  
  @media (max-width: 768px) {
    .hero h1 {
      font-size: 2rem;
    }
  }
  
  .hero p {
    font-size: 1.1rem;
    max-width: 700px;
    margin: 0 auto 30px;
    color: var(--text-light);
  }
  
  /* --- Tabs --- */
  .tabs-container {
    display: flex;
    justify-content: center;
    gap: 10px;
    margin-top: 20px;
  }
  
  .tab {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 14px 24px;
    background: rgba(255, 255, 255, 0.9);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    color: var(--text-light);
    font-weight: 600;
    text-decoration: none;
    transition: var(--transition);
    backdrop-filter: blur(10px);
  }
  
  .tab:hover {
    transform: translateY(-3px);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    color: var(--primary);
  }
  
  .tab.active {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
    box-shadow: 0 5px 15px rgba(43, 185, 191, 0.3);
  }
  
  .tab i {
    font-size: 1.1rem;
  }
  
  /* --- Donation Card --- */
  .card {
    background: var(--card);
    border-radius: var(--radius-xl);
    box-shadow: var(--card-shadow);
    padding: 40px;
    margin: 0 auto;
    max-width: 800px;
    transition: var(--transition);
  }
  
  .card:hover {
    box-shadow: var(--card-shadow-hover);
  }
  
  .card-header {
    margin-bottom: 30px;
    text-align: center;
  }
  
  .card-title {
    font-size: 1.8rem;
    font-weight: 700;
    margin-bottom: 8px;
    color: var(--text);
  }
  
  .card-subtitle {
    color: var(--text-light);
    font-size: 1rem;
  }
  
  /* --- Form Elements --- */
  .form-group {
    margin-bottom: 25px;
  }
  
  .form-label {
    display: block;
    font-size: 0.95rem;
    font-weight: 600;
    margin-bottom: 10px;
    color: var(--text);
  }
  
  .form-note {
    font-size: 0.85rem;
    color: var(--text-light);
    margin-top: 6px;
  }
  
  /* --- Frequency Toggle --- */
  .toggle-group {
    display: flex;
    gap: 10px;
    border-radius: var(--radius-md);
    background: #f8fafc;
    padding: 5px;
    width: fit-content;
  }
  
  .toggle-option {
    padding: 12px 24px;
    border: none;
    background: transparent;
    border-radius: var(--radius-sm);
    font-weight: 600;
    color: var(--text-light);
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    gap: 8px;
  }
  
  .toggle-option.active {
    background: white;
    color: var(--primary);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
  }
  
  /* --- Amount Selection --- */
  .amount-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 15px;
    margin-bottom: 15px;
  }
  
  @media (max-width: 640px) {
    .amount-grid {
      grid-template-columns: repeat(2, 1fr);
    }
  }
  
  .amount-option {
    padding: 18px 10px;
    border: 2px solid var(--border);
    border-radius: var(--radius-md);
    background: white;
    font-weight: 700;
    font-size: 1.1rem;
    text-align: center;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    flex-direction: column;
    align-items: center;
  }
  
  .amount-option:hover {
    border-color: var(--primary);
    transform: translateY(-3px);
  }
  
  .amount-option.active {
    border-color: var(--primary);
    background: var(--primary-light);
    color: var(--primary-dark);
    box-shadow: 0 5px 15px rgba(43, 185, 191, 0.15);
  }
  
  .amount-option .note {
    font-size: 0.75rem;
    font-weight: normal;
    color: var(--text-light);
    margin-top: 5px;
  }
  
  .amount-custom {
    display: flex;
    align-items: center;
    border: 2px solid var(--border);
    border-radius: var(--radius-md);
    background: white;
    overflow: hidden;
    transition: var(--transition);
  }
  
  .amount-custom:focus-within {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(43, 185, 191, 0.15);
  }
  
  .amount-custom .prefix {
    padding: 0 20px;
    font-weight: 700;
    color: var(--primary);
    background: #f8fafc;
    height: 100%;
    display: flex;
    align-items: center;
  }
  
  .amount-custom input {
    flex: 1;
    padding: 18px;
    border: none;
    font-size: 1.1rem;
    font-weight: 600;
  }
  
  .amount-custom input:focus {
    outline: none;
  }
  
  /* --- Payment Methods --- */
  .payment-methods {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 15px;
    margin-bottom: 15px;
  }
  
  @media (max-width: 768px) {
    .payment-methods {
      grid-template-columns: repeat(2, 1fr);
    }
  }
  
  @media (max-width: 480px) {
    .payment-methods {
      grid-template-columns: 1fr;
    }
  }
  
  .payment-option {
    position: relative;
  }
  
  .payment-option input {
    position: absolute;
    opacity: 0;
    width: 0;
    height: 0;
  }
  
  .payment-option label {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 20px 15px;
    border: 2px solid var(--border);
    border-radius: var(--radius-md);
    background: white;
    cursor: pointer;
    transition: var(--transition);
    text-align: center;
    height: 100%;
  }
  
  .payment-option label:hover {
    border-color: var(--primary);
    transform: translateY(-3px);
  }
  
  .payment-option input:checked + label {
    border-color: var(--primary);
    background: var(--primary-light);
    box-shadow: 0 5px 15px rgba(43, 185, 191, 0.15);
  }
  
  .payment-icon {
    font-size: 2rem;
    margin-bottom: 10px;
    color: var(--text-light);
  }
  
  .payment-option input:checked + label .payment-icon {
    color: var(--primary);
  }
  
  .payment-name {
    font-weight: 700;
    font-size: 0.95rem;
    margin-bottom: 5px;
  }
  
  .payment-desc {
    font-size: 0.8rem;
    color: var(--text-light);
  }
  
  /* --- Donor Info --- */
  .donor-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 20px;
  }
  
  @media (max-width: 640px) {
    .donor-grid {
      grid-template-columns: 1fr;
    }
  }
  
  .input-group {
    position: relative;
  }
  
  .input-group input {
    width: 100%;
    padding: 16px 20px 16px 45px;
    border: 2px solid var(--border);
    border-radius: var(--radius-md);
    font-size: 1rem;
    transition: var(--transition);
    background: white;
  }
  
  .input-group input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(43, 185, 191, 0.15);
  }
  
  .input-icon {
    position: absolute;
    left: 15px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-light);
  }
  
  /* --- Action Button --- */
  .actions {
    margin-top: 40px;
    text-align: center;
  }
  
  .submit-btn {
    background: linear-gradient(135deg, var(--accent) 0%, var(--accent-dark) 100%);
    color: var(--text);
    border: none;
    border-radius: 50px;
    padding: 18px 50px;
    font-size: 1.1rem;
    font-weight: 800;
    cursor: pointer;
    transition: var(--transition);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
    box-shadow: 0 5px 15px rgba(255, 216, 90, 0.4);
  }
  
  .submit-btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(255, 216, 90, 0.5);
  }
  
  .submit-btn:active {
    transform: translateY(-1px);
  }
  
  .submit-btn i {
    font-size: 1.2rem;
  }
  
  /* --- Receipt --- */
  .receipt-container {
    background: linear-gradient(135deg, #f0fdfa 0%, #ecfeff 100%);
    border: 2px dashed var(--primary);
    border-radius: var(--radius-lg);
    padding: 30px;
    margin-top: 30px;
  }
  
  .receipt-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 20px;
  }
  
  .receipt-title {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-dark);
    display: flex;
    align-items: center;
    gap: 10px;
  }
  
  .receipt-badge {
    background: var(--success);
    color: white;
    padding: 5px 15px;
    border-radius: 50px;
    font-size: 0.85rem;
    font-weight: 600;
  }
  
  .receipt-details {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 20px;
    margin-bottom: 25px;
  }
  
  @media (max-width: 640px) {
    .receipt-details {
      grid-template-columns: 1fr;
    }
  }
  
  .receipt-item {
    display: flex;
    flex-direction: column;
  }
  
  .receipt-label {
    font-size: 0.85rem;
    color: var(--text-light);
    margin-bottom: 5px;
  }
  
  .receipt-value {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text);
  }
  
  .receipt-actions {
    display: flex;
    gap: 15px;
    justify-content: center;
    margin-top: 30px;
  }
  
  .receipt-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 12px 25px;
    border-radius: var(--radius-md);
    font-weight: 600;
    text-decoration: none;
    transition: var(--transition);
  }
  
  .receipt-btn.print {
    background: var(--primary);
    color: white;
  }
  
  .receipt-btn.print:hover {
    background: var(--primary-dark);
  }
  
  .receipt-btn.share {
    background: white;
    color: var(--text);
    border: 1px solid var(--border);
  }
  
  .receipt-btn.share:hover {
    background: #f9fafb;
  }
  
  /* --- Error Message --- */
  .error-message {
    background: #fee2e2;
    border: 1px solid #fca5a5;
    border-radius: var(--radius-md);
    padding: 15px 20px;
    margin-bottom: 25px;
    color: #991b1b;
    display: flex;
    align-items: center;
    gap: 10px;
  }
  
  .error-message i {
    font-size: 1.2rem;
  }
  
  /* --- Progress Indicator --- */
  .progress-steps {
    display: flex;
    justify-content: space-between;
    margin-bottom: 40px;
    position: relative;
  }
  
  .progress-steps::before {
    content: '';
    position: absolute;
    top: 15px;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--border);
    z-index: 1;
  }
  
  .progress-step {
    display: flex;
    flex-direction: column;
    align-items: center;
    position: relative;
    z-index: 2;
  }
  
  .step-number {
    width: 30px;
    height: 30px;
    border-radius: 50%;
    background: white;
    border: 2px solid var(--border);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    margin-bottom: 10px;
    color: var(--text-light);
  }
  
  .step-label {
    font-size: 0.85rem;
    color: var(--text-light);
    font-weight: 600;
  }
  
  .progress-step.active .step-number {
    background: var(--primary);
    border-color: var(--primary);
    color: white;
  }
  
  .progress-step.active .step-label {
    color: var(--primary);
  }
  
  .progress-step.completed .step-number {
    background: var(--success);
    border-color: var(--success);
    color: white;
  }
  
  /* --- Loading Overlay --- */
  .loading-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(255, 255, 255, 0.9);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    z-index: 9999;
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
  }
  
  .loading-overlay.active {
    opacity: 1;
    visibility: visible;
  }
  
  .loading-spinner {
    width: 60px;
    height: 60px;
    border: 5px solid var(--primary-light);
    border-top: 5px solid var(--primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-bottom: 20px;
  }
  
  @keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
  }
  
  /* --- Footer --- */
  .footer {
    text-align: center;
    margin-top: 50px;
    padding-top: 30px;
    border-top: 1px solid var(--border);
    color: var(--text-light);
    font-size: 0.9rem;
  }
  
  /* --- Responsive Adjustments --- */
  @media (max-width: 768px) {
    .container {
      padding: 20px 15px;
    }
    
    .card {
      padding: 25px 20px;
    }
    
    .hero {
      padding: 40px 20px;
    }
    
    .tabs-container {
      flex-direction: column;
      align-items: center;
    }
    
    .tab {
      width: 100%;
      max-width: 300px;
      justify-content: center;
    }
  }
  
  @media (max-width: 480px) {
    .card {
      padding: 20px 15px;
    }
    
    .hero h1 {
      font-size: 1.8rem;
    }
    
    .submit-btn {
      width: 100%;
      padding: 18px 30px;
    }
  }