Lab
Half notebook, half playground: small things I build to understand an idea by making it move. First, a puzzle that changes every day. Below it, the newest first, are companions to posts, so you can ask the data your own question. Psst: type life, langton or turing anywhere on the site, or try the Konami code.
Puzzle of the day
Loading today's puzzle…
A new puzzle every day at midnight London time, the same for everyone. Puzzles come from a shuffled deck, so none repeats until the deck runs out. Type a guess (a percentage, a fraction or a number), then Reveal; where it can, the answer is checked by simulating the puzzle thousands of times.
Which Wren church?
Loading the chooser…
Answer yes or no to get a short list of Wren's churches to visit. Every answer is checked against the register first, so it only promises weekend hours, a café or a step-free entrance where a source published one.
Friends of the City Churches and church websites, checked 8 October 2026; Wikipedia (CC BY-SA 4.0); Historic England (OGL v3.0).
Drop a parkrun
Yellow dots are neighbourhoods more than 2 km (in a straight line) from a parkrun; blue dots are London's 65 events. Click the map to start a parkrun and see how many Londoners it brings within 2 km. Best spot (or Enter on the focused map) tries every neighbourhood centre, not just parks, so it can beat the post's park-only picks, but it has no idea whether a 5k course would fit.
parkrun events feed; ONS Census 2021 population by neighbourhood (LSOA); London Datastore boundaries. Contains National Statistics data and OS data © Crown copyright and database right.
Voronoi playground
Each cell is the patch of London closer to one plaque than to any other. Darker cells belong to plaques with a close neighbour. Click the map (or focus it and press Enter) to add a plaque, or try Random scatter to see what no clustering looks like.
Plaque locations from English Heritage, scraped August 2026 for personal, non-commercial use.
Your station's day
Blue: the station's flow per 15 minutes. Dashed: the whole network, scaled to the same peak. Hover, or focus the chart and use the arrow keys.
Powered by TfL Open Data. One modelled typical day; nothing between 02:00 and 05:00. Paddington's two Tube stations are combined here, so the list has 267 names for 269 stations.