* {
    box-sizing: border-box;
}

html{
    background-image: url("img/02.png");
    background-size: cover;
}

img {
    border: 5px solid red;
}
[class*="col-"] {
    float: left;
    padding: 5%;
}

.col-6 {
    width: 50%;
}

@media only screen and (max-width: 768px){
    [class*="col-"] {
        width: 100%;
    }
    
    html{
        background-image: url(img/03.jpg);
        background-size: cover;
        color: white;
    }
}