:host {
    display: block;
}

input.split {
    width: 25px;
    margin: 5px;
    text-align: center;
    font-size: 20px;
    color: transparent;
    box-shadow: 0px 2px 5px -2px #00000030;
    text-shadow: 0 0 0 #040404bb;
    border-color: #dcdcdcfc;
    border-width: 1px;
    border-radius: 5px;
    border-style: solid;
    outline-color: #040404bb;
    transition: 0.3s transform;
}

    input.split:focus {
        transform: scale(1.1);
        transition: 0.1s;
    }
input.first_split {
    margin-left: -7px !important;
}