Frequently asked questions

The sum of the four neighbouring fingertip distances plus thumb–little finger, in 3D, divided by your palm width and multiplied by 100. It is a unitless number: it does not depend on hand size or distance to the camera.

Because the distances are in 3D. With a flat hand you only spread fingers in one plane; if you also push some forwards and others backwards, the tips end up further apart. Try alternating: index up, middle down, ring up, little down, and the thumb as far back as it goes.

The one-second flat-hand calibration teaches the game the proportions of your hand (finger lengths and palm width). It uses them to normalise the score and to check that no hand or person is swapped during the challenge.

Not unless you choose so. The hand detector runs inside your browser and images never leave your phone. When you send a challenge you see both possible cards and choose: “Send with photo” (the real photo, exactly as taken) or “Skeleton only” (no image leaves the phone). In rooms, Settings → “What others see” decides. Those images are deleted when the challenge or room ends.

You can try, but the server recomputes the points from the pose geometry and discards hands that are not anatomically possible; manipulated scores are removed from the rankings. Attempts with two hands, a hand jump, or a hand that does not match the calibrated one are not scored. Your hand data is for your own information: cheating only fools yourself.

Yes. Detection has a noise of a few points, and your technique varies too. Good light, a plain background and a well-framed hand reduce the variation. The best of several attempts is the most reliable reference.

Any with a modern browser and a camera: Safari on iPhone (iOS 15 or later) and Chrome or Firefox on Android. On older phones the game lowers the resolution to stay smooth. The in-app browsers of Instagram, TikTok or Facebook sometimes block the camera: if that happens, open the link in Safari or Chrome.

The first time it downloads about 11 MB (the hand detector and its model). It is then stored on the phone and later games load instantly. Playing uses almost no data because images never travel.

Challenge a friend sends a link; whoever opens it plays and you compare, with rematches and rounds. In rooms everyone plays from their own phone; the creator sets capacity, admission, duration and whether play is in turns or simultaneous, and the ranking updates live. Table mode is for a single phone passed from hand to hand.

After a game you can convert your hand measurements to millimetres by holding a standard-size card (85.6 × 54 mm), a coin or a ruler next to it. The game detects the object and uses its real size as a reference.

No. Gummano is a game. It does not measure any clinical quantity, diagnoses nothing and does not replace a professional. In the science we explain what is known about hand mobility and why we find it interesting.

If you set nothing, your location is derived from your connection, without GPS; on mobile data it is sometimes your operator's city instead of yours. Fix it in Records → City → Change: it is only used for the city and country rankings.

In Settings: “Delete my games from this phone” removes the local history, and “Delete my data from the server” removes your leaderboard entry and your research records. Room and challenge data deletes itself when they end. For any other request write to info@gummano.app.

Gummano is free and sells nothing; ads pay for the servers and the development. They only appear in breaks (between games and, in Palette, between levels), never while you play. In Europe we will ask for your permission before showing personalised ads, and you can change your choice at any time.

Yes: leagues with your name, challenges of the day, custom cards. Write to info@gummano.app.