A loop spins until your device’s clock ticks, counting. How many fit is speed and load. Thrown away.

Your device has a clock that ticks about a thousand times a second. Between one tick and the next, we ask it “what time is it?” as fast as we can, and count the asks. A fast, bored machine fits in thousands; a busy or warm one fewer. So the size of this number mostly says how busy the machine is, and we do not want that. It is thrown away.

Exactly when it lands is nanosecond jitter: thermal, physical, unrepeatable. Its last bit is kept.

But whether the count lands on an even or odd number is decided by accidents of timing a billionth of a second small: the trembling of the machine’s own heat and traffic. No one can predict it, and it never repeats. That single even-or-odd is one honest coin flip, and it is all we keep.

Debiased so nothing steady can tint it, the stream should be a fair coin.

Any real coin might be slightly unfair. So before counting, every second flip is turned upside down: if something steady were tilting the coin, it would now tilt half the flips one way and half the other, and cancel itself out exactly. What survives should be pure fifty-fifty. The squares above are the real flips your device is making right now.

Summed, its wander from chance is the whole measurement.

Now count heads minus tails as the flips pour in, thousands a minute. Even a perfectly fair coin wanders a little, the way a random walk does. The gold line is that walk, live. The number beneath compares it to how far luck alone should wander: near zero is ordinary; +2σ is a wander that luck produces only about once in twenty tries; +3σ about once in three hundred. The measurement is nothing more, and nothing less, than this distance from chance.

Whether attention can lean it is the open question. Never the premise.

Everything on this site is this coin, dressed up: the music, the games, the figures are all drawn from the live walk you see above. The question the whole practice asks is simple: when a person attends, does the coin drift more than luck allows? We never assume the answer. Every sitting adds its flips to the record, one way or the other.

And this is the whole sitting: every flip since you arrived.

The gold line is the full record of this page’s coin, summed from the moment it started. The pale funnel is the reach of ordinary luck, widening as the square root of the flips: at any moment, chance alone sits inside it about nineteen times in twenty. The line is still being drawn. Whether it settles inside the funnel or walks out of it is the whole question, asked of one sitting.