* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Courier New', Courier, monospace;
    background-color: whitesmoke;
}

.caja1 {
    border: 2px black solid;
    background-color: greenyellow;
    height: 100px;
}

.caja2 {
    border: 2px black solid;
    background-color: blue;
    height: 100px;
}

.caja3 {
    border: 2px black solid;
    background-color: greenyellow;
    height: 100px;
}

.caja4 {
    border: 2px black solid;
    background-color: blue;
    height: 100px;
}

.caja5 {
    border: 2px black solid;
    background-color: greenyellow;
    height: 100px;
}

.caja6 {
    border: 2px black solid;
    background-color: blue;
    height: 100px;
}

.caja7 {
    border: 2px black solid;
    background-color: greenyellow;
    height: 100px;
}

.caja8 {
    border: 2px black solid;
    background-color: blue;
    height: 100px;
}

.caja9 {
    border: 2px black solid;
    background-color: greenyellow;
    height: 100px;
}

.caja10 {
    border: 2px black solid;
    background-color: blue;
    height: 100px;
}

@media (min-width: 30em) and (max-width: 50em) {
    .caja1 {
        height: 200px;
        background-color: rgb(73, 73, 107);
    }
}