html, body {
    margin: 0;
    padding: 0;
    background-color: black;
}

.container {
    display: flex;
    flex-wrap: wrap;
    justify-content: flex-start;
    align-content: flex-start;
    border: 20px solid black;
    background-color: black;
}

.square {
    flex-grow: 0;
    flex-shrink: 0;
    flex-basis: calc(100% / 10 - 20px);
    border-radius: 20px;
    margin: 10px;
    transition: background-color 1s;
}

@media (max-width: 600px) {
    .square {
        height: calc((100vw - 80px - 60px) / 10);
    }
}