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Interval Challenge asks you to reproduce a time interval — you are shown a duration, then asked to produce it. There is no clock to look at. It is one of the purest tests of internal timing there is, and most people discover they are systematically off in one direction rather than randomly inaccurate.
Observe the target interval being demonstrated.
Reproduce it by starting and stopping at the right moment.
Your error is shown in milliseconds, with the direction.
Rounds use different interval lengths.
Your score is your average absolute error.
Internal time estimation. Timing in the range of seconds is a genuinely separate ability from reaction speed, and personal bias — consistently short or consistently long — is stable enough to be worth knowing about. More timing games to try next: Rhythm Tap and Time Estimator. Every game in this family is on the timing games page.
Do not count. Counting turns the task into a rhythm test and your counting speed drifts with arousal.
Find your bias in the first three rounds, then correct for it. If you are consistently 200 ms short, aim 200 ms long.
Keep still. Tapping a foot or a finger gives you an external rhythm and defeats the point.
Longer intervals are harder in absolute terms and easier in percentage terms. Judge yourself on percentage error.
Time compression under attention is common — when you are engaged, intervals feel shorter than they are. Knowing your direction lets you correct it.
Stimulants are widely reported to speed up subjective time, which tends to make people produce short intervals. Test it yourself across two sessions if you are curious.
Not against any rule, but it measures your counting rather than your timing, which makes the score less interesting.
Judge it as a percentage of the target interval and track your own trend, rather than against an absolute figure.