It is said that FX was a very popular chat tool among Gu Bai's classmates, but at that time, Gu Baibai was not very interested in these things, so he never played it.
It wasn't until she went to college that she realized how powerful FX was at this time. It was FX that she met Mr. Guan...
(Fx is actually the same as yy, but, ahem, without their consent, of course the name has to be changed)