one million checkboxes, check

There was a really interesting site called One Million Checkboxes - here is a cool article about it - the technical challenges it tackled and the community of hackers who found a way to communicate (spoiler: one idea is to send messages to each other by assuming other people would figure out to try displaying stuff as a 1000x1000 grid)

I always think about the abstract problems of trying to communicate with aliens, finding the commonalities and building from there...