body {
    background: #242424;
}


#app {
    margin: 0 auto;
    display: grid;
    grid-template-rows: repeat(3, 1fr);
    grid-template-columns: repeat(4, 1fr);
    width: 800px;
    height: 600px;
    background: #c1c1c1;
    grid-gap: 10px;
}

.boks {
    background: #212121;
}

.inn {
    width: 20px;
    height: 20px;
    background: #234289;
}