body {
    font-family: 'Helvetica', 'Roboto', sans-serif;
}
.main_hero {
    background-image: url('../pictures/indexbc.png');
    background-size: cover;
}
@media only screen and (max-width: 800px) {
    .main_hero {
      background-image: url('../pictures/indexmobilebc.png');
    }
}