Reaction time test
A square turns black without warning. Tap the instant you see it.
Measured in milliseconds, and here less is better: your score is the average of every hit.
Tapping too early doesn’t cost points —there are no points to lose—: it resets the wait and stretches it, so it costs you the hit that could have been.
Fifteen seconds per run. A person who’s awake scores around 250 ms.