@media screen and (min-width: 640px) {
    .header {
        font-size: 40px;
        font-weight: bold;

    }
}
@media screen and (min-width: 360px) and (max-width: 640px) {
    .header {
        font-size: 30px;
    }
}
@media screen and (max-width: 360px) {
    .header {
        font-size: 20px;
    }
}