* {
        margin: 0;
        padding: 0;
        box-sizing: border-box;
      }
      
      body {
        font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
        background-color: var(--bg-primary);
        color: var(--text-primary);
        transition: background-color 0.3s, color 0.3s;
      }
      
      /* Header */
      header {
        background-color: var(--bg-secondary);
        border-bottom: 2px solid var(--border-color);
        box-shadow: 0 4px 15px var(--shadow);
        position: sticky;
        top: 0;
        z-index: 100;
        transition: background-color 0.3s, border-color 0.3s;
      }
      
      .header-content {
        max-width: 1400px;
        margin: 0 auto;
        padding: 12px 28px;
        display: flex;
        justify-content: space-between;
        align-items: center;
      }
      
      .logo {
        color: var(--text-primary);
        text-decoration: none;
        font-size: 24px;
        font-weight: 700;
        letter-spacing: 1px;
        transition: opacity 0.3s;
      }
      
      .logo:hover {
        opacity: 0.8;
      }
      
      .nav-links a {
        color: var(--text-primary);
        text-decoration: none;
        font-weight: 500;
        font-size: 13px;
        transition: color 0.3s;
      }
      
      .nav-links a:hover {
        color: var(--text-secondary);
      }
      
      /* Main Content */
      main {
        max-width: 1200px;
        margin: 0 auto;
        padding: 60px 40px;
        min-height: calc(100vh - 120px);
      }
      
      .page-title {
        font-size: 36px;
        font-weight: 700;
        margin-bottom: 40px;
        color: var(--text-primary);
        text-align: center;
      }
      
      /* Checkout Container */
      .checkout-container {
        display: grid;
        grid-template-columns: 1fr 1fr;
        gap: 40px;
      }
      
      .checkout-form {
        background-color: var(--bg-secondary);
        border-radius: 8px;
        padding: 40px;
        box-shadow: 0 4px 15px var(--shadow);
        border: 1px solid var(--border-color);
        transition: background-color 0.3s, border-color 0.3s;
      }
      
      .form-section {
        margin-bottom: 40px;
      }
      
      .form-section:last-child {
        margin-bottom: 0;
      }
      
      .form-section h3 {
        font-size: 18px;
        font-weight: 600;
        margin-bottom: 25px;
        color: var(--text-primary);
        padding-bottom: 15px;
        border-bottom: 2px solid var(--border-color);
      }
      
      .form-group {
        margin-bottom: 20px;
      }
      
      .form-group label {
        display: block;
        font-weight: 600;
        margin-bottom: 10px;
        font-size: 14px;
        color: var(--text-primary);
      }
      
      .required {
        color: #ff6b6b;
      }
      
      input[type="text"],
      input[type="email"],
      input[type="tel"],
      textarea,
      select {
        width: 100%;
        padding: 12px 15px;
        border: 2px solid var(--border-color);
        border-radius: 6px;
        font-size: 14px;
        font-family: inherit;
        transition: all 0.3s;
        background-color: var(--hover-bg);
        color: var(--text-primary);
      }
      
      input[type="text"]:focus,
      input[type="email"]:focus,
      input[type="tel"]:focus,
      textarea:focus,
      select:focus {
        outline: none;
        border-color: var(--text-primary);
        background-color: var(--bg-secondary);
        box-shadow: 0 0 0 3px rgba(0, 0, 0, 0.1);
      }
      
      textarea {
        resize: vertical;
        min-height: 100px;
      }
      
      /* Shipping Options */
      .shipping-options {
        display: flex;
        flex-direction: column;
        gap: 12px;
      }
      
      .shipping-option {
        padding: 16px;
        border: 2px solid var(--border-color);
        border-radius: 6px;
        cursor: pointer;
        transition: all 0.3s;
        background-color: var(--hover-bg);
        display: flex;
        align-items: flex-start;
        gap: 12px;
      }
      
      .shipping-option:hover {
        border-color: var(--text-primary);
        background-color: var(--bg-secondary);
      }
      
      .shipping-option input[type="radio"] {
        margin-top: 4px;
        width: 18px;
        height: 18px;
        cursor: pointer;
        flex-shrink: 0;
      }
      
      .shipping-option-content {
        flex: 1;
        cursor: pointer;
      }
      
      .shipping-option-name {
        font-weight: 600;
        color: var(--text-primary);
        margin-bottom: 4px;
      }
      
      .shipping-option-description {
        font-size: 13px;
        color: var(--text-secondary);
        margin-bottom: 6px;
      }
      
      .shipping-option-delivery {
        font-size: 12px;
        color: var(--text-light);
      }
      
      .shipping-option-fee {
        font-weight: 700;
        color: #ff6b9d;
        font-size: 16px;
        margin-left: auto;
        text-align: right;
      }
      
      /* Payment Method */
      .payment-options {
        display: flex;
        flex-direction: column;
        gap: 12px;
      }
      
      .payment-option {
        display: flex;
        align-items: center;
        padding: 15px;
        border: 2px solid var(--border-color);
        border-radius: 6px;
        cursor: pointer;
        transition: all 0.3s;
        background-color: var(--hover-bg);
      }
      
      .payment-option:hover {
        border-color: var(--text-primary);
        background-color: var(--bg-secondary);
      }
      
      .payment-option input[type="radio"] {
        margin-right: 12px;
        width: 18px;
        height: 18px;
        cursor: pointer;
      }
      
      .payment-option label {
        margin: 0;
        cursor: pointer;
        font-weight: 500;
      }
      
      /* Order Summary */
      .order-summary {
        background-color: var(--bg-secondary);
        border-radius: 8px;
        padding: 40px;
        box-shadow: 0 4px 15px var(--shadow);
        border: 1px solid var(--border-color);
        height: fit-content;
        position: sticky;
        top: 100px;
        transition: background-color 0.3s, border-color 0.3s;
      }
      
      .summary-title {
        font-size: 18px;
        font-weight: 600;
        margin-bottom: 25px;
        color: var(--text-primary);
        padding-bottom: 15px;
        border-bottom: 2px solid var(--border-color);
      }
      
      .summary-items {
        margin-bottom: 25px;
        max-height: 300px;
        overflow-y: auto;
      }
      
      .summary-item {
        display: flex;
        justify-content: space-between;
        padding: 12px 0;
        border-bottom: 1px solid var(--border-color);
        font-size: 14px;
        color: var(--text-secondary);
      }
      
      .summary-item:last-child {
        border-bottom: none;
      }
      
      .summary-item-name {
        color: var(--text-primary);
      }
      
      .summary-item-price {
        font-weight: 600;
        color: var(--text-primary);
      }
      
      .summary-totals {
        padding: 20px 0;
        border-top: 2px solid var(--border-color);
      }
      
      .summary-row {
        display: flex;
        justify-content: space-between;
        padding: 8px 0;
        font-size: 14px;
        color: var(--text-secondary);
      }
      
      .summary-row.total {
        font-size: 18px;
        font-weight: 700;
        color: var(--text-primary);
        padding-top: 15px;
        border-top: 2px solid var(--border-color);
        margin-top: 15px;
      }
      
      .summary-row.total .amount {
        color: var(--accent);
      }
      
      .btn {
        width: 100%;
        padding: 10px 24px;
        border: none;
        border-radius: 6px;
        font-weight: 600;
        cursor: pointer;
        transition: all 0.3s;
        font-size: 14px;
        text-decoration: none;
        display: flex;
        align-items: center;
        justify-content: center;
        gap: 8px;
        text-transform: uppercase;
        letter-spacing: 0.5px;
        margin-top: 10px;
      }
      
      .error-message {
        background-color: #ffebee;
        color: #c62828;
        padding: 15px 20px;
        border-radius: 6px;
        margin-bottom: 25px;
        border-left: 4px solid #c62828;
      }
      
      /* Footer */
      footer {
        background-color: #000;
        color: #fff;
        padding: 40px;
        border-top: 2px solid #333;
        margin-top: 60px;
      }
      
      footer p {
        font-size: 14px;
        color: #aaa;
      }
      
      @media (max-width: 768px) {
        .header-content {
          padding: 10px 14px;
        }

        main {
          padding: 18px 14px;
        }
        
        .page-title {
          font-size: 24px;
          margin-bottom: 18px;
        }
        
        .checkout-container {
          grid-template-columns: 1fr;
          gap: 16px;
        }

        .checkout-form,
        .order-summary {
          padding: 18px;
          border-radius: 8px;
        }

        .form-section {
          margin-bottom: 22px;
        }

        .form-section h3,
        .summary-title {
          font-size: 15px;
          margin-bottom: 12px;
          padding-bottom: 10px;
        }

        .form-group {
          margin-bottom: 12px;
        }

        .form-group label {
          font-size: 12px;
          margin-bottom: 6px;
        }

        input[type="text"],
        input[type="email"],
        input[type="tel"],
        textarea,
        select {
          padding: 9px 10px;
          font-size: 13px;
          border-width: 1px;
        }

        textarea {
          min-height: 72px;
        }
        
        .order-summary {
          position: static;
          top: auto;
        }
        
        .shipping-option {
          flex-wrap: wrap;
        }
        
        .shipping-option-fee {
          width: 100%;
          text-align: left;
          margin-left: 0;
          margin-top: 10px;
        }
      }

      /* Mobile Phone Styles (< 480px) */
      @media (max-width: 480px) {
        .header-content {
          padding: 8px 10px;
        }

        main {
          padding: 14px 10px;
        }

        .page-title {
          font-size: 20px;
          margin-bottom: 14px;
        }

        .checkout-container {
          gap: 12px;
        }

        .checkout-form {
          padding: 12px;
          border-radius: 8px;
        }

        .form-section {
          margin-bottom: 14px;
        }

        .form-section h3 {
          font-size: 14px;
          margin-bottom: 10px;
          padding-bottom: 8px;
        }

        .form-group {
          margin-bottom: 10px;
        }

        .form-group label {
          font-size: 11px;
          margin-bottom: 5px;
        }

        input[type="text"],
        input[type="email"],
        input[type="tel"],
        textarea,
        select {
          padding: 8px 9px;
          font-size: 12px;
          min-height: 38px;
        }

        textarea {
          min-height: 64px;
        }

        /* Shipping Options */
        .shipping-options {
          gap: 8px;
        }

        .shipping-option {
          padding: 9px;
          flex-direction: column;
          align-items: flex-start;
        }

        .shipping-option input[type="radio"] {
          margin-top: 0;
          margin-bottom: 8px;
        }

        .shipping-option-name {
          font-size: 12px;
        }

        .shipping-option-description {
          font-size: 11px;
        }

        .shipping-option-delivery {
          font-size: 10px;
        }

        .shipping-option-fee {
          font-size: 12px;
          margin-top: 6px;
        }

        /* Payment Options */
        .payment-options {
          gap: 8px;
        }

        .payment-option {
          padding: 9px;
        }

        .payment-option input[type="radio"] {
          width: 16px;
          height: 16px;
          margin-right: 10px;
        }

        .payment-option label {
          font-size: 12px;
        }

        /* Order Summary */
        .order-summary {
          padding: 12px;
          border-radius: 8px;
        }

        .summary-title {
          font-size: 14px;
          margin-bottom: 10px;
          padding-bottom: 8px;
        }

        .summary-items {
          max-height: 170px;
          margin-bottom: 10px;
        }

        .summary-item {
          padding: 7px 0;
          font-size: 12px;
        }

        .summary-totals {
          padding: 10px 0;
        }

        .summary-row {
          padding: 6px 0;
          font-size: 12px;
        }

        .summary-row.total {
          font-size: 14px;
          padding-top: 8px;
          margin-top: 8px;
        }

        .btn {
          padding: 10px 12px;
          font-size: 12px;
          min-height: 40px;
        }

        .error-message {
          padding: 9px;
          font-size: 12px;
          margin-bottom: 10px;
        }
      }