* {
    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: rgb(76, 76, 76);
        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: lightcoral;
        grid-template-columns: repeat(2, 1fr);
    }
    .caja{
        background-color: lightyellow;
        
    }
}
@media (min-width: 901px) {
    .caja-padre {
        background-color: lightgreen;
        grid-template-columns: repeat(4, 1fr);
    }
    .caja{
        background-color: lightblue;
        
    }
}