.calculator {
    background: #fff;
    border: 1px solid #ddd;
    border-radius: 10px;
    padding: 25px;
    width: 400px;
    box-shadow: 0 3px 8px rgba(0,0,0,0.1);
}
h2 {
    font-size: 18px;
    color: #1a3d7c;
    margin-bottom: 15px;
}
label {
    display: block;
    margin-top: 12px;
    font-size: 14px;
}
input {
    width: 100%;
    padding: 8px;
    margin-top: 4px;
    border: 1px solid #ccc;
    border-radius: 5px;
}
.radio-group {
    margin-bottom: 15px;
}
.radio-group label {
    display: inline-block;
    margin-right: 15px;
}
.btn {
    background: #1a3d7c;
    color: #fff;
    padding: 10px 20px;
    margin-top: 15px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-size: 15px;
}
.btn:hover {
    background: #163267;
}
.result {
    margin-top: 15px;
    font-weight: bold;
    color: green;
}