#container {
    width: 600px;
    border: 1px solid #000;
}

.flexbox {
    display: flex;
}

.block {
    border: 1px solid #000;
    /* padding: 10px; */
    flex: 1;
    aspect-ratio: 1 / 1;
}

.colored {
    background-color: #000;
}