.mapStyle {
    border-radius:5px;
    border-style:solid;
    border-color:red;
    border-width:2px;
    height:400px;
    margin-left:auto;
    margin-right:auto;
    max-width:400px;
    width:100%;
}

@media only screen and (max-width:800px) {
    /*tablet or below*/
}

@media only screen and (max-width:600px) {
    /*phone or below*/
    .mapStyle {
        height:300px;
        max-width:400px;
    }
}

@media only screen and (max-width:400px) {
    /*phone or below*/
    .mapStyle {
        max-width:300px;
    }
}