How to Play Reaction Time
Reaction Time is a straightforward reflex test with no tricks in it. The screen shows red and you wait. After a random delay it turns green, and you tap, click or press space as quickly as you can. The game measures the gap in milliseconds between the colour change and your input. Tap while the screen is still red and you fail that round — the delay is randomised specifically so you cannot learn it and pre-empt it.
Over five rounds the game gives you both your best single time and your average, which together tell you far more than either number alone.
Controls
Tap, click, or press Space the instant the screen turns green. Any of the three works, though which one you choose does affect your result slightly — more on that below.
What the numbers actually mean
Human visual reaction time is remarkably consistent across the population. For a simple visual stimulus like a colour change, most adults land somewhere between 200 and 300 milliseconds, with around 250ms being typical. Under 200ms is genuinely fast. Under 150ms almost always means you anticipated the change rather than reacted to it — which the red-screen fail condition is there to discourage.
For context, that quarter of a second is not wasted time. It is the light hitting your retina, the signal travelling to your visual cortex, your brain recognising the change, a motor command being generated, and that command travelling down your arm to your finger. Most of the delay is transmission, not decision.
Why your average matters more than your best
It is tempting to focus on the single fastest number you have ever hit, but one fast result can easily be a partial guess that happened to land after the colour changed. Your five-round average is much harder to fake and much more representative of what your reflexes actually do.
If your best time is dramatically faster than your average — say 140ms best against a 280ms average — that gap is usually a sign that you are occasionally anticipating rather than reacting.
Small things that change your result
Hand position. If your finger is resting on the key or hovering over the screen before the round begins, you save the time it takes to move into position. If your hand is in your lap, you are measuring arm movement, not reaction.
Input device. A mouse click and a key press are close. A touchscreen tap is typically a little slower because of screen input latency. Even your monitor adds a few milliseconds before the green actually appears. None of this is worth worrying about unless you are comparing your result to someone on different hardware.
Focus mode. Staring hard at the centre of the screen feels like it should help, but tense over-focusing tends to slow people down. Relaxed, open attention gives better results for most people.
What actually affects your reflexes
Reaction time is one of the more measurable ways your general state shows up as a number. Sleep debt, dehydration, alcohol and a heavy meal all slow it, often by 30 to 50 milliseconds — a change large enough to see clearly in a five-round average. Warming up helps too: almost everyone is faster on their second attempt than their first.
Age matters as well. Reaction time is fastest in the late teens and early twenties and slows gradually after that. It is also trainable, but only within limits. You can recover the gap between your tired self and your rested self; you cannot train your way past the speed of nerve conduction.
Plays on any device
The reaction test runs in your browser using HTML5 and works on phones, tablets, laptops and desktops. Nothing to install, no signup, and your best times are stored locally in your browser.
