A three-digit number flies across the screen. Read it. Each correct answer makes the next one faster; three misses and you are out

Dynamic vision is not eyesight

You can read the bottom line of an eye chart and still score low here. Static acuity is how small a still object you can resolve; dynamic visual acuity is how accurately you can read something in motion. It combines smooth pursuit (the eyes tracking a target), saccades (snapping focus to a new spot) and how fast the brain processes a brief image. It improves with training and it is one of the first things to decline with age.

LEVEL 12	Pro batter — the "seeing the seams on a fastball" range
10–11	Table-tennis or badminton player
8–9	Goalkeeper, combat sports
6–7	Above average; road signs are easy at speed
4–5	Typical adult
1–3	Common when tired or on a small screen

How to read it

Do not chase the number. At the fast levels your eyes cannot keep up if you try to follow it. Look at the centre of the screen and read the afterimage as it passes — this is what athletes mean when they say the ball "arrives" rather than being watched. Holding the three digits as a single shape and matching it against the choices also helps.

What affects the result

Refresh rate matters a lot. On a 60 Hz screen the number is only drawn for a handful of frames at the top levels, which makes it harder than it should be; 120 Hz is noticeably clearer. Compare scores on the same device. Small screens shorten the travel distance, and fatigue easily costs two or three levels — try it in the morning and again at night.

It trains

Baseball and racquet-sport players work on this deliberately. Reading moving text, reading licence plates as cars pass, simple catch — a few weeks of any of it shows up here. Playing this once a day is enough to watch your level climb.

How to play

1. Press START. The screen goes dark with a small crosshair in the centre — keep your eyes there.
2. "Ready…" appears, and somewhere between 0.7 and 1.2 seconds later a three-digit number flies from left to right. The delay is different every time.
3. Once it has passed, four choices appear: the answer plus three numbers that differ from it by exactly one digit.
4. A correct pick flashes lime and raises the level; a miss flashes pink and puts out one heart. Level and remaining hearts stay visible at the top.
5. When all three hearts are gone, the result screen shows your level, grade and top speed, with a nickname box for the leaderboard.

Levels and speed

The number takes 1.30 seconds to cross the screen at LEVEL 1, and each level cuts that time by 17%. The crossing time does not depend on screen size; the digits scale with the screen instead. Three fading copies trail behind the number as motion blur.

LEVEL	Crossing time	LEVEL	Crossing time
1	1.30 s	7	0.43 s
2	1.08 s	8	0.35 s
3	0.90 s	9	0.29 s
4	0.74 s	10	0.24 s
5	0.62 s	11	0.20 s
6	0.51 s	12	0.17 s

The "top speed" on the result screen is the crossing time of the last level you passed. On a 60 Hz display the LEVEL 12 number is on screen for roughly ten frames.

Scoring and the leaderboard

Your score is the last level you passed. A miss never lowers the level — it only costs a heart — so five correct answers followed by three misses ends at LEVEL 5. There is no level cap, so it keeps getting faster as long as you keep up. Reaching the end of your limit ends the run at the maximum of 12. Your personal best is kept on the device, and the global Top 10 on the title screen ranks by level. Anyone with LEVEL 1 or higher can submit with just a nickname of up to 12 characters; there is no account.

Frequently asked questions

I never see the number at all

The pause after "Ready…" is there to catch wandering eyes; stay on the crosshair. The first few levels take over a second, so if nothing registers there, the screen is usually too dim or the browser window very narrow.

Why are the choices so similar?

Each wrong choice changes exactly one of the three digits. It forces you to have read all three — if you tend to catch the first two and guess the last, you will miss even at low levels.

What do I need to get on the leaderboard?

A nickname. Type up to 12 characters in the box under the result and tap Submit; your current rank appears straight away. A run that ends at LEVEL 0 (no correct answers) does not show the box.

Can I compare phone and desktop scores?

The crossing times are identical, but screen size and refresh rate are not, so compare against yourself on one device. The leaderboard does not separate devices — treat it as a reference.

Related tools

• Reaction Time Test — how quickly you respond once you have seen something
• Aim Trainer — eyes and hand working together for accuracy
• Sequence Memory Test — remembering what you briefly saw
• Color Vision Test — the eye's other job: colour rather than motion