CouponCodeInput.css

.quiqqer-coupons-field {
    float: left;
}

div + .quiqqer-coupons-field {
    margin-left: 20px;
}

.quiqqer-coupons-couponcodeinput {
    display: flex;
    padding: 5px;
}

.quiqqer-coupons-couponcodeinput button {
    border-radius: 0 3px 3px 0;
}

.quiqqer-coupons-couponcodeinput input {
    border-radius: 3px 0 0 3px;
    line-height: 36px;
}