body {
    text-align: center;
}

#button {
    display: flex;
    justify-content: center;
    margin: 0 auto;
    width: 10%;
    text-decoration: none;
    text-align: center;
    border: 4px solid black;
    color: black;
    padding: 5px;
    border-radius: 5px;
    transition: .5s;
    font-weight: bold;
}

#button:hover {
    border: 4px solid red;
    color: red;
    background-color: black;
}