Full Circle

draw one circle freehand, all the way round

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Draw a circle on the sheet with one stroke, all the way round to where you started, and lift. Six circles make a round. The reveal holds a moment so you can study it; a quick tap jumps to the next one, and a press you keep down holds the reveal for as long as your finger does — the pause is a floor, not a clock.

Anywhere on the sheet, any size you like. Every tolerance here is a plain fraction of your own circle’s radius, with no pixel floor under it, so the same shape scores the same at any size: scale one attempt up or down and the number does not move. What size does change is the drawing, not the marking — your hand’s wobble is a fixed number of pixels, so it is a bigger fraction of a small circle, and drawing big is genuinely easier. The one size rule is a refusal: a circle whose radius is under a tenth of the sheet’s short side, and never under 40 px, is too small for the drill to measure honestly. That costs you nothing.

Ran out of trackpad or glass halfway round? Lifting early does not score. The drill says how far round you got and draws a dashed ring where you stopped: press inside it and the same circle carries on. A stroke that covers less than four fifths of a turn is never graded at all.

Scored on how far your line strays from the truest circle that can be drawn through it, measured as a fraction of that circle’s own radius and averaged along the line rather than over the samples, so drawing part of it faster barely moves the mark — under a point, even at a hard flick. Up to 45 points come off for a gap where the line should have closed; running past your own start is the cheaper mistake and the first tenth of a turn of overlap is free. The round is the average of the six.

The reveal draws that true circle over your line, marks the point of widest drift with a dot and a dash, and puts the score in the middle. The dotted band around it is where the score runs out. Then it says what actually went wrong — flat on the left, closing early, drifting wide as you come back round — graded against the same tolerance as the number, so the words and the score never disagree. At the end of the round, if every circle went flat in the same place, it says so: that is the habit to fix, not any one circle.

The drill grades against the hardware it detects (shown in the corner as “scoring for …”), because the same wobble means different things from a mouse, a finger and a pen. Your score is only ever compared with your own.

Studio tip: swing from the shoulder, not the wrist or the fingers. Move the pen in the air above the paper a few times first, then drop it in on the same path — and keep your eye on the point you started from, not on the tip.

Drawing a circle freehand, and finding out why it is not one

A blank sheet. Draw a circle on it with one stroke — anywhere, any size — all the way round to where you began, then lift. Six of them make a round, roughly forty seconds. Your last two attempts stay faintly behind the new one, because redrawing over your own last try is the studio warm-up the whole thing is built out of.

Almost nobody is bad at circles evenly. The hand goes flat in one place, and which place depends on your grip and on whether the stroke comes from the wrist or the shoulder — a wrist runs out of arc partway round and the line straightens for a moment. So the drill draws the truest circle through your line, marks where you strayed furthest from it, and names the miss in ordinary words: flat on the left, you close early, it drifts out as you come back round. At the end of the round, if every circle went flat in the same place, it says so — six circles with the same flat spot are one habit, not six mistakes.

How it is scored

The scoring is not a model or a stored answer. It is closed-form geometry, computed on your device from the points your stroke passed through: a least-squares circle is fitted to them, and the score is the RMS distance from your line to that fitted circle, divided by its radius.

Averaged along the line, which is the part that takes some care. Your digitizer samples on a clock — 120 to 1000 times a second — so the number of samples in a stretch of line says how long your hand spent there, not how much line there is. Anything averaged by counting samples is therefore an average over time: whipping through a flat spot would put it in the mean a third as often as the arc beside it, and the same shape would score higher for being drawn unevenly. Both the fit and the RMS weight every sample by the length of line it stands for instead, so the mark is the same however fast any part of it was drawn, and the same at any digitizer rate.

Under 1.2% of the radius is a clean 100; the roundness score reaches zero at 13% of the radius, multiplied by 1.0 for a pen, 1.5 for a finger and 2.0 for a mouse or trackpad, because a wrist pivoting a mouse cannot creep the way a nib can. Those percentages are the whole band — there is no pixel floor under them — so a small circle and a large one really are held to the same standard, and a scaled copy of an attempt scores the same to the last decimal. Circles too small to measure that way are refused rather than graded kindly. Closing counts too: the arc you leave missing costs up to 45 points, and a stroke covering less than four fifths of a turn is not scored at all — the drill offers to carry it on instead.

⭕ Full Circle

Drawing a circle freehand, and finding out why it is not one

How it is scored

Full Circle