.container div {
    /* width: 100px;
    inline-size: 100px; */
    height: 100px;
    block-size: 100px;
    text-align: center;
    line-height: 100px;
}

.container {
    border: 1px solid currentColor;
    display: flow-root;
}

div.box1 {
    background-color: sandybrown;
    float: left;
    width: 100px;
    inline-size: 100px;
}
div.box2 {
    background-color: skyblue;
    height: auto;
    block-size: auto;
    line-height: 1;
}
div.box3 {
    background-color: lightgreen;
    clear: left;
    /* margin-top: 20px;
    margin-block-start: 20px; */
    width: 200px;
    inline-size: 200px;
    float: right;
}
div.box4 {
    background-color: yellow;
    width: 300px;
    inline-size: 300px;
    float: right;
}