header {
    width: 100%;
    height: 99%;
}
@media screen and (min-width: 0px) and (max-width: 750px){
    header {
        width: 100%;
        height: 99.5%;
    }
}

header .hero {
    position: relative;
    width: 100%;
    height: 100%;
    z-index: 0;
}

/* logo */
header .hero .logo {
    position: absolute;
    width: auto;
    width: 31vw;
    bottom: 30vh;
    left: 5vw;
    z-index: 4;
    -webkit-transition: all 1.5s ease-in-out;
    -moz-transition: all 1.5s ease-in-out;
    -o-transition: all 1.5s ease-in-out;
    transition: all 1.5s ease-in-out;
}

header .hero::after {
    content: '';
    display: block;
    position: absolute;
    top: 0;
    height: 80vh;
    width: 35vw;
    z-index: 3;
    left: 3vw;
}