partedInput.css

.parted-input {
    border: 0;
    background-image: linear-gradient(to left, black 45%, rgba(255, 255, 255, 0) 0%);
    background-position: bottom;
    background-size: 50px 1px;
    background-repeat: no-repeat;
    background-position-x: -21px;
    text-align: center;
    max-width: 40px;
}
.parted-input.square {
    border-width: 1px;
    border-style: solid;
    border-color: black;
    margin-right: 5px;
    width: 30px;
    height: 30px;
    background-image: none; 
    background-position: bottom;
    background-size: 50px 1px;
    background-repeat: no-repeat;
    background-position-x: -21px;
    text-align: center;
}

.parted-input:focus {
    outline: none;
}

.parted-input::-webkit-inner-spin-button,
.parted-input::-webkit-outer-spin-button {
    -webkit-appearance: none;
    margin: 0;
}