The Double A Method

                                          /*==================================================    The Double A Method==================================================*/ * {
    box-sizing: border-box;
}
 body {
    border-left-color: red;
    border-left-style: solid;
    border-left-width: 8px;
}
 @media only screen and (min-width: 30em) {
    body {
        border-left-color: orange;
    }
}
 @media only screen and (min-width: 40em) {
    body {
        border-left-color: green;
    }
}
 @media only screen and (min-width: 50em) {
    body {
        border-left-color: blue;
    }
}
 @media only screen and (min-width: 60em) {
    body {
        border-left-color: purple;
    }
}