Nim’s Lantern Gate: a short, calm focus game

Nim the hedgehog keeps a little gate in the evening. Visitors come one at a time, each carrying a lantern, and a sign shows which lantern to look for. You make one choice: open the gate, or wait. Waiting earns a light just like opening does. A session is three short parts, about three minutes, and then it ends by itself. It is free, for kids and grown-ups, with nothing to install. It is a game, not a medical treatment.

How to play

1. Look at the sign: it shows one lantern and a tick or a cross.
2. A tick means open only for that lantern. A cross means open for every lantern except that one.
3. Tap the button or the picture to open the gate, or just wait and let the visitor walk on.
4. Every right choice lights a light, and waiting counts as much as opening.
5. After three short parts the session ends and one more star joins your sky.

Controls

• Tap the big button or the picture to open the gate. To wait, do nothing at all.
• Keyboard: Space or Enter opens the gate, Escape pauses.
• Calm mode removes the stars, glows and floating lights. Sound is off until you switch it on. With your device set to reduce motion, visitors appear beside the gate instead of walking.

Tips and strategy

• Look at the sign first: the tick means “only this lantern”, the cross means “all except this lantern”.
• Lanterns differ in color, shape and marks, so you never have to rely on color alone.
• There is no need to rush. Speed is not scored, and you can decide any time before the visitor reaches the gate.
• A wrong choice costs nothing. The next visitor simply comes along, and the pace eases a little.
• In part three the sign changes every few visitors. Nim tells you when it happens, and the next visitor waits a moment.
• When the session ends, stopping is the plan. Stars in your sky never fade, however long you stay away.

Game modes and difficulty

Part one asks you to open only for the lantern on the sign. Part two is the opposite: open for all except that lantern. In part three the sign changes as you go. The game adjusts itself: after three right choices in a row it gets a little harder, with a quicker pace and more alike lanterns, and after one miss it eases, so it aims for about four right out of five. There is no timer on screen and no way to lose.

History and background

The idea comes from simple tasks that researchers have used for decades to study attention, where a person responds to some signs and holds back on others. We used research on attention and ADHD to shape the design: short sessions, one thing at a time, immediate and kind feedback, no flashing, a quiet mode and a clear ending, with no streaks or daily rewards.

We also read what the research does not support. Large reviews found that computer-based training makes people better at the trained tasks, but has little or no effect on ADHD symptoms when the people rating them do not know who took part. So we make no such promise. Everything is drawn in code, and your stars and pace history stay in your browser.

Frequently asked questions