* {
    box-sizing: border-box;
}

body {
    background-color: steelblue;
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100vh;
    margin: 0;
}

.empty {
    height: 150px;
    width: 150px;
    margin: 10px;
    border: solid 3px black;
    background-color: #fff;
}

.fill {
    background-image: url('https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRtJpvXflqD9aMCPf_ckcjbEuYAxsy70Y55MQ&s');
    width: 145px;
    height: 145px;
}

.hold {
    border: solid 5px #ccc;
}

.hovered {
    background-color: #333;
    border-color: #fff;
    border-style: dashed;
}

@media (max-width: 768px) {
    body{
        flex-direction: column;
        flex-wrap: wrap;
    }
}