How to play
Everyone watches the duck. After a random wait, from about two to five seconds, it quacks and the screen lights up. The first person to tap after that wins the round. Tap before the quack and you’re out of that round, so don’t guess. Play 5 or 10 rounds; whoever wins the most rounds wins the duel.
One phone or online
On one phone, two people sit facing each other with the phone flat between them. The top half of the screen is turned round for the player across the table; each of you taps your own half. On a keyboard, the keys are A and L. Online (when it’s available), 2 to 8 people each play on their own phone. Each phone times its own player from the moment the quack shows on that screen, so a slow connection doesn’t cost anyone the round.
Tips
Most people react to a sight in about 200 to 250 milliseconds. Rest a finger just above the screen, look at the middle of it rather than the duck, and don’t try to time the wait: it’s random every round. A time under 90 milliseconds counts as a guess, not a reaction. For a solo challenge, try the reaction test.