Know exactly
how sharp you are

Your attention is the one thing you use every waking second and have never once been able to see. You know you're sharper some days than others. You've never known by how much.

Five real tests. Reaction times to the millisecond. A baseline built from your own performance, not a population average dressed up as a score. Nobody has ever handed you this before — not your doctor, not your smartwatch, and definitely not a tile-matching game with a "brain age" generator bolted on.

A letter appears every couple of seconds. Hit Match when it's the same as the one N steps back. One-back is a warm-up. Three-back breaks people. You're holding a moving window in your head and rewriting it every two seconds while the next letter is already coming.

Exactly how much you can hold and update at once before it falls apart. Most people find their ceiling faster than they expect, and it is lower than they'd like to admit.

The level you can hold is your number. Anyone can luck into one good round. Sustaining 3-back at 80%+ accuracy is a genuinely elite piece of mental hardware, and the app will tell you the moment you get there.

Green means tap. Red means don't. Sounds like nothing — until the app stacks the deck with green until tapping is automatic, then throws a red at you. Your finger is already moving. Can you stop it?

The exact moment your speed outruns your control. Tap a red and that's a commission error — an impulse that got through. Miss a green and that's an omission error — attention dropped out. Push one down and the other climbs. The app tracks both separately, which is the only way this number means anything.

Fast with clean reds is the session worth having. Fast with rising commission errors just means you traded control for speed, and most apps would have congratulated you for it. This one tells you.

Signal appears. You respond. Nothing to memorize, nothing to outthink — just the raw distance between seeing and acting, measured in milliseconds.

The purest read on your current state in the whole app. No strategy to hide behind. And the number that matters most isn't your average — it's your consistency. A rock-steady 400ms and an average of 400ms built from 300s and 600s are two completely different brains on the day. Only one of them is running clean.

Run this one daily. It's the mode that responds hardest to how you slept and what you did last night, which makes it the sharpest instrument you own for catching your own state.

Odd or even. Then without warning — high or low. Same digits on screen, completely different question, and the rule you were running two seconds ago is now working against you.

Your switch cost — the precise millisecond penalty your brain pays every time it has to drop one rule and load another. Everyone has one. Almost nobody has ever seen theirs. This app puts a number on the exact thing that happens to you every time you get pulled off a task.

Your switch cost against your own switch cost. Absolute values shift with task design, so a number from here isn't comparable to a lab paper or another app — but the trend in your data is exact, and it's yours.

The word says RED. The ink is green. Name the ink. Your brain has been reading automatically since you were six years old and it will not stop just because you asked it to. You can feel the collision happen.

Your congruency effect — the millisecond cost of overriding an automatic response. That gap is one of the few places you can directly watch your own cognitive control working, in real time, as a number.

Watch the congruency effect, not your overall accuracy. The congruent trials are easy for everybody — they're padding. The gap is the signal.

Open any other brain app and try to find out how the score is calculated. You can't, because there's nothing to find. Here's ours, in public.

Every comparison is built from your baseline, at your difficulty level, in that mode. Difficulty scales as you improve, so comparing a hard session against an easy one would be garbage — we handle that. A "brain age" scored off a population average tells you nothing about you.

A pattern needs at least five days on each side before this app will say a word about it, and it has to clear a statistical significance test with a correction applied for testing several things at once. Below that bar you get told exactly how many more days it needs. Every other app would have shown you a chart and let you draw the wrong conclusion.

If your caffeine days and non-caffeine days look identical, this app tells you they look identical. That answer is worth money and nobody else in this category will ever give it to you, because their entire product is telling you something happened.

"I feel a bit off today" becomes "I'm 94ms off my baseline." That is the entire difference between a vague sense and a fact, and you get it in about three minutes.

Sleep, alcohol, illness, time of day — these move reaction time and attention, and that's well documented. What's never existed is your version of it. Log your days, run your sessions, and the app puts your numbers side by side and shows you what your body actually does. Not a study average. Yours.

Weeks of millisecond-precision data on your own cognition, on your phone, that no doctor's visit and no wearable on the market is collecting for you.

Time of day moves reaction time on its own, so a session at 9am and one at 11pm aren't comparable. Lock in a slot and your data gets dramatically sharper. Three minutes is enough.

Everything is computed per mode and per level, so spreading yourself across all five gives you five shallow datasets instead of one powerful one. Choice RT and Stroop react hardest to your daily state — start there.

Six taps before a session. That's the difference between a scoreboard and an instrument, and it's what unlocks the patterns that make this app worth having.

Your first sessions are you learning the task, not you. Around day ten the baseline settles and the numbers start telling you things you didn't know. That's when this gets addictive.