Sky Puzzle

for iPhone and iPad · by Tom Bakx

Sky Puzzle is an astronomy puzzle built from real telescope data: put each ALMA galaxy image back where it belongs on the Herschel sky. It is also playable in a browser at tombak.xyz/skypuzzle.

Support

Questions, bugs or ideas: email skypuzzle@tombak.xyz. It helps to say which device you use and what you were doing when it went wrong.

The sky does not line up with the real one.: The direction the phone faces comes from its compass, which is often 5–35° out, worst indoors and near metal. The dashed circle shows how far off it may be. Sweep the phone in a figure of eight to calibrate it, or drag the sky with one finger until a bright star you can see sits in the right place. The correction stays as you move.
Pointing mode says location is off.: The app needs your rough position to work out which part of the sky is overhead. Turn it on in Settings › Sky Puzzle › Location, then tap ◎ in the app. You can play the whole game without it on the flat map.
How do I reset the game?: Reset in the top bar clears the board. It never clears your high scores.

Privacy policy

Last updated 26 September 2026.

Sky Puzzle collects no data. The app makes no network connections: it has no accounts, no analytics, no advertising and no third-party code that talks to a server.

Location: If you allow it, the app uses your approximate location, together with the compass and motion sensors, to work out which part of the sky the phone is pointing at. This happens entirely on your device. Your location is never stored and never sent anywhere. You can refuse or withdraw permission at any time in Settings, and the game stays fully playable on the map.
Game progress and high scores: These are kept in the app's own storage on your device. They are not sent anywhere and are deleted when you delete the app.
Buying me a coffee: The optional tip is an in-app purchase handled entirely by Apple, under Apple's privacy policy. I receive no personal information about you from it, and it unlocks nothing: the game is the same with or without it.
Links: Some in-game notes link to research papers. Opening one hands the link to your web browser, and that website's own privacy policy then applies.
Children: The app collects no information from anyone, including children.
Changes and contact: If this ever changes, this page will be updated before the app is. Questions: skypuzzle@tombak.xyz.

Credits

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. The maps are from the H-ATLAS and HerMES surveys. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSTC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. Star, constellation and Milky Way data: d3-celestial © Olaf Frohn, MIT licence.