.app-header {
    display: flex;
    flex-direction: column;
    flex-wrap: wrap;
}

.app-header__col-a,
.app-header__col-b,
.app-header__col-c {
    align-items: center;
    overflow: hidden;
}

.app-header__col-a { display: flex; }
.app-header__col-b { display: flex; }
.app-header__col-c { display: none; }

@media (min-width: 768px) {
    .app-header { flex-direction: row; }
    .app-header__col-a { display: flex; }
    .app-header__col-b { display: flex; }
    .app-header__col-c { display: flex; }
}

@media (min-width: 1024px) {
    .app-header { flex-wrap: nowrap; }
    .app-header__col-a { order: 1; }
    .app-header__col-b { order: 3; }
    .app-header__col-c { order: 2; }
}