feture

Use CSS variable-position: absolute;z-index: 2; and CSS3 variable-:root,( --primary-color:), background: var(--primary-color,red);@media screen and (max-width:600px)

 This is CSS sheet (z-index)

#styld{

    background: var(--color-2,green);

    height: 250px;

    width: 250px;

    position: absolute;

    z-index: 2;

}

#styla{

    background: var(--primary-color,red);

    height: 250px;

    width: 250px;

    position: absolute;

    left: 150px;

    z-index: 1;

}

/* css3 vribal */

:root{

        --primary-color: rgb(179, 24, 24);

        --color-2: rgb(26, 26, 2);

}

@media screen and (max-width:600px){

    :root{

       

        --primary-color: black;

        --color-2: yellow;}

}

This is HTML sheet <div clear>

<div>

<div id="styld"></div>

<div id="styla"></div>

</div>

<div class="div-clear"></div>