.quantity-control {
    display: flex;
    align-items: center;
    justify-content: center;
}
.quantity-control button {
    width: 30px;
    height: 30px;
    font-size: 20px;
    line-height: 1;
    text-align: center;
    background: #eee;
    border: 1px solid #ccc;
    cursor: pointer;
    padding: 0;
}
.quantity-control .quantity-input {
    width: 50px;
    height: 30px;
    text-align: center;
    border: 1px solid #ccc;
    border-left: none;
    border-right: none;
    -moz-appearance: textfield; /* Firefoxで矢印を非表示 */
}
.quantity-control .quantity-input::-webkit-inner-spin-button, 
.quantity-control .quantity-input::-webkit-outer-spin-button {
    -webkit-appearance: none; /* Chrome, Safariで矢印を非表示 */
    margin: 0;
}