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best flag rule
(sh.itjust.works)
Be sure to follow the rule before you head out.
Rule: You must post before you leave.
Personally I'm a fan of Botswana's flag. Despite using very simple shapes only three colours, it's still instantly recognisable - I'm pretty sure it'd be distinct even in greyscale, or even if you just saw the three colours at all because nobody else uses that pale blue alongside white and black.