*{
    box-sizing: border-box;
}

header{
    width: 90%;
    margin: 20px auto;
    font-size: 4vw;
    text-transform: capitalize;
    color: darkgray;
    border-bottom: 15px double lightgray;
}

article, footer, main{
    width: 90%;
    margin: 20px auto;
}

footer{
    color: grey;
}

ul{
    display: flex;
    flex-wrap: nowrap;
}

li{
    list-style-type: none;
    width: 23%;
    font-size: 1.2vw;
    padding: 3px 10px;
    border-right: 3px solid lightgray;
}

li:last-of-type{
    border: none;
}

li > img{
    margin: 0px 2px;
}

span{
    color: blue;
}

main{
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
}

img[alt="principal"], section{
    width: 90%;
    margin: 10px auto;
}

h2{
    width: 100%;
    font-size: 2vw;
}

section{
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
}

section > img{
    width: 50%;
    border: 1px solid grey;
    margin: 15px 0px;
}

img[alt="notas"],img[alt="twi"],img[alt="mail"]{
    display: none;
}

@media screen and (min-width: 576px){
    img[alt="notas"],img[alt="twi"]{
    display: inline;
    }

    section{
        justify-content: center;
    }

    section > img{
    width: 33%;
    border: 1px solid grey;
    margin: 15px 0px;
    }
}

@media screen and (min-width: 1000px){
    img[alt="mail"]{
        display: inline;
    }

    main{
        flex-wrap: nowrap;
    }

    section > img{
        width: 45%;
        border: 1px solid grey;
        margin: 15px 0px;
    }

    img[alt="principal"]{
        margin: 20px;
    }
}