Flip-flops are also acceptable. I also saw many people wearing flip-flops in the park. But don't wear slippers worn at home. No matter whether someone is in charge or not, it always looks bad.

Clothes? Don't wear pajamas and vest. Everything else is ok.

In fact, no one cares, but you always look bad if you dress too untidily. . .

PS: There are many people in the park, and shopping is very tiring. It's best to travel light, bring an empty kettle and have more irrigation points. It's much easier than bringing drinks, and drinks don't have to go through security inspection. . .