CSS立方体覆盖

:root{
    --black: rgb(11, 14, 17);
    --green: rgb(112, 228, 80);
    --gray: rgb(55, 55, 55);
}

*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body{
    width: 100%;
    height: 100%;
    background-color: var(--black);
    color: #eee;
}

#rect-bar{
    width: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    border-radius: 15px;
    overflow: hidden;
}

#rect-bar .rect-row{
    width: 100%;
    height: 150px;
    display: flex;
    flex-direction: row;
    align-items: center;
    justify-content: center;
    /* border: 1px solid white; */
}

#rect-bar .rect-row .rect-cube{
    margin: 5px;
    width: 150px;
    height: 150px;
    border-radius: 15px;
    background-color: var(--green);
    /* border: 1px solid white; */
}

#rect-bar .rect-row .rect-cube.rcg{
    width: 120px;
    height: 120px;
    background-color: var(--gray);
}

<div id="rect-bar">
  <div class="rect-row">
    <div class="rect-cube rcg">
    </div>
    <div class="rect-cube">
    </div>
  </div>
  <div class="rect-row">
    <div class="rect-cube">
    </div>
    <div class="rect-cube rcg">
    </div>
  </div>
</div>