@media (max-width:768px){

.header{

    flex-wrap:wrap;
}

.nav{

    display:none;
    position:absolute;
    top:100%;
    left:0;
    width:100%;
    background:#837f7f;
}

.nav.active{

    display:block;
}

.nav ul{

    flex-direction:column;
}

.hamburger{

    display:block;
}

.banner{

    padding:30px 15px;
}

.banner__title{

    font-size:2rem;
}

.principal{

    padding:20px 10px;
}

.section__item{
    flex:1 1 100%;
    max-width:350px;
}

.plataforma{
    width:100%;
}
}

@media (max-width:768px){

    .principal{
        flex-direction:column;
    }

    .section__item{
        width:100%;
    }
}