Test your reaction speed over five rounds. Tap the instant the screen turns from red to green and bring your five-round average down — every millisecond counts.
Tap anywhere on the screen to start a set of five rounds. A row of five dots above the prompt tracks your progress, and the round number (1/5, 2/5 …) is shown below it.
Each round begins on a dark red screen that says "Wait for green…". After a random pause of one to four seconds the whole screen turns green and shows TAP! — touch it as fast as you can. Your time for that round appears in large numbers for about 0.6 seconds, then the next red screen starts by itself.
Touching the screen while it is still red is a false start. The screen says "Too soon!" and that round is recorded as a 2,000 ms penalty; the set carries on, but the penalty stays in your average. Taps made while a result or the "Too soon!" message is on screen are ignored — only a tap on the red "Wait for green…" screen counts as a false start.
The timer for each round starts on the animation frame that draws the green screen, not at the moment the game decides to switch colours, so the wait for your phone's next screen refresh is not added to your time.
After the fifth round you see your average, the five individual times (penalties in red) and your best average on this device. Lower is better. Save score sends the average to the Hall of Fame, which ranks the ten lowest five-round averages; tap anywhere else to start a new set straight away.
Most of your time is decided before green appears, by how ready your hand is. Hover your thumb just clear of the glass over the middle of the screen: any contact while you are waiting for green counts as a false start, so resting the thumb on the glass is not an option, but a few millimetres of travel is. Because the entire screen changes colour, there is no spot you need to watch — a relaxed gaze at the centre catches the change as well as a hard stare and is less tiring across five rounds.
The biggest score killer is anticipation. Green arrives after a random delay, so trying to guess the exact moment leads to taps on a red screen. Treat every round as if green could come a beat later than you expect and let the colour trigger your finger, not your prediction. On a phone, a clean average of 200–250 ms is a strong result; a single round far below that is usually a guess that happened to land just after the switch, and the same guess next round will cost you 2,000 ms.
Do the arithmetic before you gamble. Your score is the plain average of five rounds, so shaving 20 ms off one round improves it by only 4 ms, while one false start adds 2,000 ms to the total — 400 ms on the average. Four clean 250 ms rounds plus one false start average 600 ms, twice as slow as five careful 300 ms rounds. No amount of guessing pays that back.
Know how the wait is built. The red pause is drawn evenly between one and four seconds, so green never comes in the first second and always arrives before the fourth one ends. As a red screen drags on, green really is getting closer, and that is exactly when an eager thumb fires a fraction too soon — a tap 50 ms before green costs the same 2,000 ms as a tap in the first second. Use the opening second to settle your hand, then wait for the colour, however overdue it feels.