Green Light
A free reaction time game. A red light stays on for a length of time you cannot predict, turns green, and you tap as fast as you can. Tapping too early simply restarts the wait.
- Free
- No ads
- No account
- No download
- Works offline
- Single player
How do you play?
- Pick a level - Easy, medium or hard. What changes is how hard the moment is to predict.
- Start - The light goes red and an unpredictable wait begins.
- Wait - Do not tap. An early tap starts a fresh wait and costs nothing.
- Tap on green - As fast as you can. The screen shows your time in milliseconds.
About this game
Red light. You wait. It turns green, and you tap.
The wait has to be unpredictable or the number that comes out is not a reaction time, it is a score for guessing well. So what is guessing actually worth here? We measured it. If a child stops watching and taps at a fixed moment, the best fixed moment available is the middle of the band, and they will miss it by an average of 400 milliseconds on easy, 675 on medium and 951 on hard. That last one is nearly a full second of error against a real reaction of about half a second. Guessing does not pay.
Which is why the levels widen rather than lengthen. The easy band runs from one second to 2.6, and the hard band from 1.2 to five. The average wait grows only 1.72 times between them while the width of the band grows 2.38 times. The skill being trained is holding still through uncertainty, not sitting for longer.
Tapping before green is not a loss. The light says not yet and starts a fresh wait, and there is no failure state in this game to arrive at. The fresh wait also cannot be very short, so a child mashing the screen cannot accidentally land a tap that gets recorded as a fast reaction.
Every result is praise. Under 350 milliseconds is lightning, under 550 is quick, under 900 is good, and everything else is steady. There is no rating for too slow, because a five-year-old's reaction is nowhere near an adult's quarter of a second and there is no reason to tell them so.
What does it teach?
Withholding a response
Most of this game is not moving. That is self control, and it trains exactly like speed does.
Sustained attention
Five seconds watching a screen that does not change is a long time, and it stretches with age.
Understanding measurement
The number is a real time in milliseconds, and children enjoy trying to improve it.
That mistakes are free
An early tap is not punished, so a child learns to try again rather than to become overly careful.
Tips
Watch, do not count
Counting in your head feels like planning and is exactly what the game neutralises. The best possible guess misses by almost a second on hard.
Keep your finger close
The distance your hand travels is part of the time. A finger hovering above the screen saves tens of milliseconds.
Relax between attempts
A tense shoulder slows a reaction down. Two attempts after a short rest beat six in a row.
Start on easy
A narrower band gives your attention less room to wander. After a few there, hard makes sense.
What age is it for?
4 to 5
Easy. Five seconds of waiting is a lot at this age, and the narrow band helps.
6 to 8
Medium. This is where improving the number becomes the point.
9 and up
Hard, with the widest band.
Adults
An adult's simple visual reaction is around 250 milliseconds. Under 350 counts as lightning here too.
Accessibility
One tap anywhere on the screen, with no dragging and no small target to hit. The light differs by shape and position as well as hue, so colour blindness does not affect knowing when to respond. Nothing flashes quickly, no sound is required, and the change to green is a single transition rather than a flicker. An early tap produces no error sound. There is no time limit on the response itself, and every result gets a kind word.
Playing together
Take turns
Ten attempts each and compare averages. An average is fairer than a best.
Child against adult
The adult almost always wins, so play for who improves most across ten attempts instead.
No looking at your hand
Eyes on the light only. You find out how much you were watching your finger.
Guess the wait
Before each attempt, guess how long the red will last. Nobody is close, which is the whole point.
Common questions
Is the game free?
Completely. Nothing to pay and no purchases inside the game. Every game on the site is open from the first second.
Do I need to download or sign up?
No to both. It runs in the browser with no download and no account, and we do not ask for an email.
What happens if my child taps before green?
The light says not yet and starts a fresh wait. No score drops, and this game has no failure state at all.
Can you predict when the light will change?
Not usefully. Guessing at the best possible moment still misses by an average of 400 milliseconds on easy and 951 on hard. A real reaction is faster than that.
Are there ads?
None. No banners and no video between levels.
Does it work offline?
Yes. After one visit the game is stored on the device and runs on a plane.
What is a good reaction time for a child?
An adult reaches about 250 milliseconds on a simple visual reaction and a five-year-old is a long way from that. Every result here is praised, and under 900 already counts as good.
What is the difference between the levels?
The width of the wait band. Easy runs one second to 2.6 and hard runs 1.2 to five. The average only grows 1.72 times while the width grows 2.38 times, because the skill is standing still through uncertainty.
What age is this for?
From about four on easy. There is no reading anywhere and the only requirement is waiting and then touching.
Does it collect data about my child?
No. There is no signup and no name. No session recording and no behavioural advertising. We count how many times a game was opened, with nothing attached that identifies who opened it.