No not really....casual is ok
No mix bagged some dressed some very casual.
Dress casual
You certainly don't, but you'd probably feel out of place rolling in in your couch clothes. Tends to be a trendy or professional crowd.
You won't feel out of place if you dress formally but you also won't be turned away for four dressing down.
No rule there that I know of. Dress for your own occasion.
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