div.row div {
    border: 1px solid #eee;
}

div#jt{
    border: 10px double darkgray;
}

/*--------- MEDIA QUERIES ----------*/
@media (min-width:200px) { /*200 and bigger*/
    
    div#jt{
        border: 10px solid red;
    }
}/*end 200px min-width styles*/


@media (min-width: 400px) {/*400 and bigger*/
    /*small phone*/
    
    div#jt{
        border: 10px solid orange;
    }
    
}/*end 400px min-width styles*/

@media (min-width: 600px) {/*600 and bigger*/
    
    div#jt{
        border: 10px solid yellow;
    }
    
}/*end 600px min-width styles*/


@media (min-width: 800px) {/*800 and bigger*/
    /*iPhone XMax landscape*/
    /*iPadPro portrait*/ 
    
    div#jt{
        border: 10px solid green;
    }
    
}/*end 800px min-width styles*/

@media (min-width: 1200px) {/*1200 and bigger*/
    /*iPad Pro landscape*/
    
    div#jt{
        border: 10px solid blue;
    }
    
}/*end 1200px min-width styles*/


@media (min-width: 1400px) {/*1400 and bigger*/
    
    div#jt{
        border: 10px solid indigo;
    }
    
}/*end 1400px min-width styles*/

@media (min-width: 1600px) {/*1600 and bigger*/
    /*large desktop mac*/
    
    div#jt{
        border: 10px solid violet;
    }
    
}/*end 1600px min-width styles*/