*{
    box-sizing: border-box;
}

body{
    background-color: white;

}

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

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

}
footer{
    color:b grey;
}

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

}
li{
    list-style-type: none;
    font-size: 1.2vw;
    width: 20%;
    padding:3px 10px;
    border-right: 1px solid black;
}
li:last-of-type{
    border: none;

    
}
li > img{  
    margin:0px 10px;
}
span{
    color:blue;
} 
main{
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
}
img[alt="principal"], section{
    width: 90%;

}
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: 10px 0px;

}

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


@media screen and (min-width: 576px){
    img[alt="stu"]{
    display: inline;
    }
    section{
        justify-content: center;
    }
    section > img{
    width: 33%;
    border: 1px solid grey;
    margin: 10px 0px;

}
}
@media screen and (min-width: 993px){
    img[alt="twi"], img[alt="mail"]{
        display: inline;

}
@media screen and (min-width: 1000px){
    main {
        flex-wrap: nowrap;
    }
 }
 img[alt="principal"] {
    width: 150px;
 }
}