The core idea is, you draw a circle on a satellite view map and it tells you the population inside + more info.The home page is a daily challenge, I ve backfilled some past challenges so there s more than just the past couple of days to play, and there is also a free-draw mode that tells you population + some census demographic info points-of-interest data from OpenStreetMap.In most cases, the data comes from taking the census blocks w/ centroids contained in your circle and summing their population. Demographic info is slightly more complex as it s not sourced on blocks, so we allocate population-weighted fractions of a source territory s published census values into the drawn territory. Happy to answer any questions about the data or the technical side. The game/app only covers US areas at the moment, I d like to add international data in the future!I am re-submitting this as a proper Show HN , as I left the Show HN text out of the title the last time I submitted