.kitap-hesaplayici {
            max-width: 600px;
            margin: 0 auto;
            padding: 20px;
            background: #f9f9f9;
            border-radius: 8px;
            box-shadow: 0 0 10px rgba(0,0,0,0.1);
            font-family: Arial, sans-serif;
        }
        .form-group {
            margin-bottom: 15px;
        }
        .form-group label {
            display: block;
            margin-bottom: 5px;
            font-weight: bold;
            color: #333;
        }
        .form-control {
            width: 100%;
            padding: 12px;
            border: 1px solid #ddd;
            border-radius: 4px;
            font-size: 16px;
            box-sizing: border-box;
        }
        .checkbox-option {
            margin: 12px 0;
            display: flex;
            align-items: center;
        }
        .checkbox-option input[type="checkbox"] {
            margin-right: 10px;
            transform: scale(1.2);
        }
        .checkbox-option label {
            margin: 0;
            font-weight: normal;
            cursor: pointer;
        }
        .button-group {
            display: flex;
            gap: 10px;
            margin-top: 20px;
            flex-wrap: wrap;
        }
        .btn-pdf {
            background: #2271b1;
            color: white;
            border: none;
            padding: 15px 20px;
            border-radius: 4px;
            cursor: pointer;
            font-size: 16px;
            flex: 1;
            transition: background 0.3s;
            min-width: 120px;
        }
        .btn-ekle {
            background: #4CAF50;
            color: white;
            border: none;
            padding: 15px 20px;
            border-radius: 4px;
            cursor: pointer;
            font-size: 16px;
            flex: 1;
            transition: background 0.3s;
            min-width: 120px;
        }
        .btn-red {
            background: #f44336;
            color: white;
            border: none;
            padding: 15px 20px;
            border-radius: 4px;
            cursor: pointer;
            font-size: 16px;
            flex: 1;
            transition: background 0.3s;
            min-width: 120px;
        }
        .btn-pdf:hover {
            background: #135e96;
        }
        .btn-ekle:hover {
            background: #3e8e41;
        }
        .btn-red:hover {
            background: #d32f2f;
        }
        .toplam-fiyat {
            margin: 25px 0;
            font-size: 1.3em;
            padding: 20px;
            background: #f0f0f0;
            border-radius: 4px;
            text-align: center;
            border: 2px solid #ddd;
        }
        .custom-option {
            margin-top: 25px;
            padding-top: 20px;
            border-top: 2px solid #ddd;
        }
        .custom-option h4 {
            margin-bottom: 15px;
            color: #333;
            font-size: 1.2em;
        }
        #pdf-error {
            padding: 12px;
            background: #ffebee;
            border-radius: 4px;
            margin-top: 15px;
            text-align: center;
        }
        #kayit-bilgi {
            padding: 12px;
            background: #d4edda;
            border-radius: 4px;
            margin-top: 15px;
            text-align: center;
        }
        .bold-text {
            font-weight: bold;
        }
        
        /* Mobil uyumluluk */
        @media (max-width: 768px) {
            .kitap-hesaplayici {
                margin: 10px;
                padding: 15px;
                border-radius: 6px;
            }
            .form-control {
                padding: 14px;
                font-size: 16px;
            }
            .button-group {
                flex-direction: column;
            }
            .btn-pdf, .btn-ekle, .btn-red {
                padding: 16px;
                font-size: 16px;
                width: 100%;
            }
            .toplam-fiyat {
                font-size: 1.4em;
                padding: 15px;
                margin: 20px 0;
            }
            .checkbox-option {
                margin: 15px 0;
            }
            .checkbox-option input[type="checkbox"] {
                transform: scale(1.4);
                margin-right: 12px;
            }
        }
        
        @media (max-width: 480px) {
            .kitap-hesaplayici {
                padding: 12px;
                margin: 5px;
            }
            .form-group label {
                font-size: 16px;
            }
            .btn-pdf, .btn-ekle, .btn-red {
                font-size: 16px;
                padding: 14px;
            }
            .toplam-fiyat h3 {
                font-size: 1.2em;
                margin: 0;
            }
        }
        
        .form-control:focus {
            outline: none;
            border-color: #2271b1;
            box-shadow: 0 0 5px rgba(34, 113, 177, 0.3);
        }
        
        .btn-pdf:focus, .btn-ekle:focus, .btn-red:focus {
            outline: none;
            box-shadow: 0 0 5px rgba(34, 113, 177, 0.5);
        }