Reflex Grid

React to the right cell as fast as you can — while decoys sit beside it and the rule itself keeps changing. Five modes, five rule variants, a grid that adapts to how you are playing, and a daily pattern that is the same for everyone.

Mode

One cell lights up. Tap it. Nothing else is asked of you.

No Classic Targets session recorded yet.

Classic Targets — press Start when you are ready.

How to play

Press Start, then wait. After a short, deliberately uneven pause, cells light up on the grid. Tap the one the rule asks for — which is written above the board, and is written there before the cells appear, so reading it is never part of what is being timed.

Some rules put decoys beside the answer. One rule asks you not to tap at all: leave the amber diamond alone and you are credited for holding.

On a keyboard, press a cell's letter to tap it — A is the top left — and Space to hold.

Two rules worth knowing before you start

Tapping before the cells appear costs you the trial. The wait is a different length every time, so there is nothing to anticipate — and a tap under 100 ms after the cells appear counts as early too, because it was launched before there was anything to see.

Your score is not your reaction time. Each trial banks the part of its window you did not use. A trial you let expire banks nothing; a wrong cell costs a whole trial's worth. Your median reaction time is reported beside the score, because it is the most useful thing to compare against yourself — but a score made of medians would reward answering only the easy trials.

Modes

Classic Targets: — one lit cell, tap it; nothing else is asked of you
Go / No-Go: — tap the teal circles and leave the amber diamonds alone — withholding is scored
Colour-Rule Switch: — the rule changes between trials: match a colour, match a shape, or find the odd one out
30-second Sprint: — thirty seconds, and as much banked speed as you can hold on to
Daily Pattern: — one fixed schedule for everybody, every UTC day, mixing all five rules

Each mode keeps its own best. The scores are not comparable across modes — Go / No-Go spends some of its trials on cells you are meant to leave alone, and those pay less than a hit — so one number across all five would tell you that you had got worse when you had only changed mode.

Tips

Read the rule during the wait, not when the cells appear. It is on screen the whole time for exactly that reason.
In Go / No-Go, the cost of one wrong tap is larger than the gain from several fast ones. Slowing down slightly is usually the higher-scoring choice.
Look at the middle of the grid rather than hunting cell by cell. On a five-wide board, scanning is most of the time you spend.
If a trial is already lost, let it go rather than tapping something. A miss banks nothing; a wrong cell costs a whole trial.

Privacy and local play

Everything runs in your browser. Your bests, your daily results, your settings and your reaction-time distribution are kept in this browser's local storage and are never sent anywhere — there is no account, no server and no leaderboard. The trials are generated on your own device and the sounds are synthesised there too; nothing is downloaded. Clearing this game's data removes all of it and touches nothing else on Zerdly.

Frequently asked questions

I tapped as the cell appeared and it said I was too early. Is that right?: Yes. A tap before the cells appear, or one faster than 100 milliseconds after they do, is recorded as a false start and scores as a wrong cell. Nobody sees, decides and moves in under a tenth of a second, so a tap that fast was launched before there was anything to react to. Without the rule, the quickest way to a perfect score would be to hammer the board through the wait.
Why is my score not my reaction time?: Because a score that was your reaction time would reward you for not playing. Answer only the trials that feel easy and let the hard ones expire, and your median gets better while you do less — we measured it: a player answering 29 of 300 targets posts the fastest median in the game. So each trial instead banks the part of its window you did not use, a trial you let expire banks nothing, and a wrong cell costs a whole trial. Your median is still reported, right next to the score; it is just not the thing you are chasing.
Is this the same as the Aim Trainer or the Reaction Time Test?: No, and the difference is the decoys. The Aim Trainer has no wrong targets at all — every circle is one you want. The Reaction Time Test has one signal and you always respond. Reflex Grid puts wrong cells on the board and, in Go / No-Go, asks you to sometimes not respond at all, which is a different skill from moving fast. The Colour-Rule Switch mode goes further and changes the rule between trials.
The grid changed size in the middle of my session.: That is the difficulty controller. It watches how much of each window you are actually using and moves the grid, the time and the number of lit cells together, in small steps and in both directions. Answer comfortably and it grows; start missing and it eases off. The Daily never adapts, so that everybody gets the same challenge.
I switched apps for a moment and it says my session does not count.: A session that leaves the screen cannot be compared with one that did not, so it stops being eligible for a personal best. It is not thrown away: the trials still count towards your lifetime reaction-time distribution, and you can finish the session normally. The alternative — ending the run outright — would punish you for taking a phone call.
Can I play without a mouse or a touchscreen?: Yes, and it is not a lesser mode. Every cell has a letter; press it to tap that cell, which is one keystroke per answer — the same count as one click. Press Space to hold deliberately, which is how you answer a No-Go cell without waiting it out. The letters appear on the board as soon as you use a key.
I am colour-blind. Can I play the Colour-Rule Switch mode?: Yes. Every colour carries its own pattern — solid, striped, dotted or cross-hatched — and the rule names both, so “tap the teal one” also reads as “tap the solid one”. Colour and shape are independent, so the shape rule never depends on hue either, and Go and No-Go cells differ in shape as well as colour.
Why does no sound play when the cells appear?: Because it would quietly become the thing you were reacting to. With a sound at that moment you answer whichever signal reaches you first, which makes a session with sound on and one with sound off two different games under a single best. In Go / No-Go it is worse: a cue that told Go from No-Go would hand you the answer, and one that did not would be a pure go signal. So every sound here plays after a trial has already resolved.
Why is there no leaderboard?: There is no server and no account, so there is nobody to compare you with. Your bests and your distribution live in this browser and nowhere else. We would rather show you your own distribution tightening over weeks than invent a rank.