html,
body {
    margin: 0px;
    padding: 0px;
    background-color: cornflowerblue;
    font-size: 18px;
}

h1 {
    font-size: 3rem;
    color: #fff;
}

.contenedor {
    width: 100%;
    height: 100%;
    margin: 0px auto;
    background-color: burlywood;
    text-align: center;
    display: flex;
    flex-direction: row;
    gap: 2%;
    justify-content: space-between;

}

.caja1 {
    background-color: blueviolet;
    color: aliceblue;
    border: 10px solid #000;

}

.caja2 {
    background-color: rgb(43, 61, 226);
    padding: 25px;
    color: aliceblue;
    border: 10px solid #000;
}

.caja3 {
    background-color: rgb(43, 214, 226);
    padding: 25px;
    box-sizing: border-box;
    color: #000;
    border: 10px solid #000;

}

@media screen and (min-width: 1240px) and (max-width: 1300px) {

    html,
    body {
        background-color: rgb(237, 187, 100);
    }
}

@media screen and (max-width: 1240px) {

    html,
    body {
        background-color: rgb(237, 100, 207);
    }
}

@media screen and (min-width: 980px) and (max-width: 1040px) {

    html,
    body {
        background-color: rgb(100, 228, 237);
    }
}

@media screen and (max-width: 980px) {

    html,
    body {
        background-color: rgb(100, 237, 155);
    }

    .contenedor {
        flex-direction: column;
    }

}