Start a hidden stopwatch and stop it as close as you can to a target between 3 and 15 seconds. No clock is shown — how precise is your inner timing?
Each round shows a target time at the top of the screen, picked at random between 3.0 and 15.0 seconds in steps of a tenth — 7.3s, for example. Next to it, Best shows the smallest error you have ever made on this device.
Tap the big blue START button and begin counting in your head. The button turns red and its label changes to STOP, but the running time is never shown. Tap STOP when you think the target time has passed.
The result shows your actual time and how far off you were, both to a hundredth of a second — for example "Actual: 7.46s" and "Off by: 0.16s". Stopping early and stopping late are scored the same way: only the size of the error matters, and smaller is better.
Every round stands on its own. Tap the green AGAIN button for a new target, or New in the top bar to draw a different target before you press START. Save score sends that round's error to the Hall of Fame, which ranks the ten smallest errors.
Because the counter is hidden, this is a test of internal rhythm, not eyesight. Pick a counting method and use the exact same one every round — many players count "one-thousand-one, one-thousand-two", but a steady song lyric or a tapped beat is often more stable. Consistency is everything; an internal clock that runs slightly fast is fine as long as it runs fast by the same amount each time.
Note your error after each attempt and adjust by feel, not by overcorrecting. If you stopped at 6.8 against a 7.3 target, you were a touch quick, so add a hair of patience rather than doubling your count. Avoid holding your breath or tensing up, since stress speeds your internal sense of time and makes you stop early almost every round.
Use the Actual line to measure your own beat. If you counted exactly eight beats for an 8.0s target and the result reads "Actual: 8.80s", each of your beats lasts about 1.1 seconds. For the next target, divide by that length — 5.5 seconds is five of your beats — rather than trying to speed up or slow down your count, which is much harder to control than how many beats you count. Measure again every few rounds, because your beat drifts with mood and tiredness.
Judge each miss as a share of its target. Timing errors tend to grow with the length of the interval, so missing a 15.0s target by 0.30s is as precise as missing a 3.0s target by 0.06s — both are 2%. Best and the Hall of Fame look only at the raw error, whatever the target was, so your smallest errors are most likely to come on short targets, while long targets are the better test of a steady count. If you want to practise one length on purpose, New draws a different target before you start.