.container {
    max-width: 600px;
    margin: auto;
    padding: 20px;
    border: 1px solid #ccc;
    border-radius: 10px;
    background-color: #f9f9f9;
}

h2 {
    text-align: center;
}

.form-group {
    margin-bottom: 15px;
}

label {
    font-size: 16px;
}

input[type="number"], button {
    padding: 10px;
    font-size: 16px;
    width: 100%;
    margin-top: 10px;
}

.result {
    margin-top: 20px;
    padding: 15px;
    background-color: #e0ffe0;
    border: 1px solid #c1e6c1;
    text-align: center;
    display: none; /* 初期は非表示 */
}

.result-box {
    padding: 10px;
    background-color: #f0f0f0;
    border: 1px dashed #aaa;
    text-align: center;
    margin-top: 20px;
}