How come my font changes in ´.box´ but not my ´.red-box´ class?

Question

https://code.sololearn.com/WkNgKFmdlrvN/?ref=app
In My CSS I played around with what features work where and apparently 30px font works best in my ´.box´ class. But in ´.red-box´ the ´font-size: 30px;´ doesn't work AND by box shrinks vertically. I just don't understand. Please break this down. Yes I borrowed this from FreeCodeCamp

Answer 1

That is because you mentioned font-size: 10px; in box class