div:hover{
    background-color: #a9a9a9;
    align-items: center;
}
body{
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    background-color: gray;
}
button :active
{
background-color: black;
transition: 5ms;
}