How it works

A 10-second game with your phone camera: how far apart can you get your fingertips… in 3D. No sign-up, nothing to install.

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Calibration (1 second). Show your hand open and flat, palm facing the camera, fingers slightly apart, about a hand's length away. Place it inside the outline and hold still until the ring fills. This is how the game learns the proportions of your hand.
Challenge (5 seconds). A countdown starts. Spread and twist your fingers: some up, some down, as far from each other as you can. The pose you are holding when it hits 0 is the one that gets scored.
Result. You see your points and your photo with the hand skeleton, and you can challenge a friend, play with several people in a room, or check the records by city, country and world.

What the score measures

A hand detector locates 21 points of the hand in every frame, with an estimated depth. The score is the sum of the four 3D distances between neighbouring fingertips (thumb–index, index–middle, middle–ring, ring–little) divided by the width of your palm:

points = 100 × (d₁ + d₂ + d₃ + d₄) / palm width

Dividing by palm width puts big and small hands on an equal footing: what counts is flexibility and technique, not size. And because the distances are in 3D, moving fingers forwards and backwards adds as much as opening them in the plane of the palm. That is why a flat, stretched hand is not the best pose.

Tips

The rear camera is used by default: point it at your other hand. The button at the top right switches to the front camera.
Good light and a plain background help the detector. Avoid fingers hiding each other.
Play as many times as you like. Your best score is kept on this phone and, if you allow it, on the leaderboard.
The game checks that the hand in the calibration is the same as in the challenge: switching hands or people mid-way invalidates the attempt.

Your hand in numbers

After each game you can see the geometry of your hand drawn over your own photos: relative length of each finger, widths, angles between fingers and the shape of the palm. Hold a card, a coin or a ruler next to your hand and the game converts the measurements to millimetres.

With friends

Challenge a friend: a link is sent via WhatsApp (or any app). Whoever opens it plays and you compare; there are rematches and multi-round matches.
Rooms: everyone plays from their own phone. The person who creates the room sets the capacity, who gets in, how long it lasts and whether play is in turns or simultaneous. The ranking updates live.
Table mode: a single phone passed from hand to hand, in turns.

More in the FAQ and in the science behind the game.