How to play
Each round begins after a random delay. Keep your pointer or finger ready, but only click when the central target turns green. Your five valid reaction times are averaged at the end.
Reaction-time tips
Use the same device when comparing scores because mouse, touchscreen, browser and display latency can change the measured time. Relax your hand, focus on the center signal and avoid anticipating the green state.
Frequently asked questions
How is reaction time measured?
The game records the browser's high-resolution timer when the signal becomes active and when your click or tap is received, then reports the difference in milliseconds.
Why did I get a false start?
You clicked while the signal was still in the waiting state. The random delay changes every round to make prediction harder.
Can I play with touch?
Yes. Tap directly inside the game area.