.dgk-installment-box {
    padding: 20px;
    border: 2px solid #1565C0;
    border-radius: 10px;
    background: #f9fbff;
    box-shadow: 0 4px 10px rgba(0,0,0,0.08);
    max-width: 420px;
}

.dgk-installment-box h3 {
    margin-bottom: 12px;
    color: #1565C0;
    font-size: 18px;
    font-weight: bold;
}

.dgk-installment-box label {
    display: block;
    margin-bottom: 12px;
    font-size: 14px;
}

.dgk-installment-box input,
.dgk-installment-box select {
    width: 100%;
    box-sizing: border-box;
    padding: 8px;
    margin-top: 5px;
    border: 1px solid #ccc;
    border-radius: 6px;
    font-size: 14px;
}

#calc-result {
    margin: 12px 0;
    padding: 12px;
    background: #fff;
    border: