#is-calculator {
    border: 2px solid #ccc;
    padding: 15px;
    max-width: 450px;
    margin: 20px auto;
    border-radius: 8px;
    background: #fdfdfd;
}
#is-calculator input, #is-calculator button {
    width: 100%;
    margin-top: 10px;
    padding: 8px;
    font-size: 1em;
}
#is-result table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 15px;
}
#is-result th, #is-result td {
    border: 1px solid #ccc;
    padding: 8px;
    text-align: center;
}
#is-result th {
    background-color: #f0f0f0;
}