.calculator-box {
    border: 2px solid #ddd;
    background: #f9f9f9;
    padding: 15px;
    margin-bottom: 20px;
    border-radius: 10px;
    box-shadow: 0 0 8px rgba(0,0,0,0.1);
}
.calculator-box h3 {
    margin-top: 0;
    color: #2a7ae2;
}