*{
    margin: 0;
    padding: 0;
}

body{
    font-family: Verdana, Geneva, Tahoma, sans-serif;
}

h2{
    color: blueviolet;
}

.caja-padre{
    padding: 1em;
    display: grid;
}

.caja{
    margin: 1em;
    
}

@media (max-width:600px) {
    .caja-padre{
        background-color:gray;
        grid-template-columns: repeat(1, 1fr);
       
    }
    .caja{
        background-color: rgb(255, 255, 255);
    }
    
}

@media (max-width:900px) and (min-width:601px) {
    .caja-padre{
        background-color: rgb(255, 255, 141);
        grid-template-columns: repeat(2, 1fr);
    }
    .caja{
        background-color: orange;  
    }
}

@media (min-width:901px) {
    .caja-padre{
        background-color: greenyellow;
        grid-template-columns: repeat(4, 1fr);
    }
    .caja{
        background-color: rgb(21, 255, 0);
        
    }
}