Perfect Circle

How to play

Draw a circle in one stroke with your mouse or finger. The game measures how far every point of your line strays from a perfect ring and scores you from 0 to 100 percent. A dashed ghost circle then appears over your attempt so you can see exactly where you wobbled. Tiny doodles are rejected, so give it a proper sweep.

Tips

• Draw big. The score compares wobble to your circle's size, so the same hand jitter hurts less on a large ring.
• Move fast and smooth, swinging from the shoulder. Slow, careful strokes collect more jitter.
• Keep one steady speed all the way around. Speeding up mid-stroke flattens the arc, and that is what tanks scores.
• Close the loop. A big gap shifts the measured center and drags the whole shape away from round.

How the score is calculated

The game does not compare your line to some ideal circle it drew first. It finds the centre of the shape you drew, measures how far every point on your line sits from that centre, and works out how much those distances vary. A perfect circle has every point at exactly the same distance, so zero variation is 100 percent. The more your line wobbles in and out, the lower the score.

That has two consequences. First, size does not matter directly, because the variation is measured relative to your average radius, so a big circle and a small circle with the same proportional wobble score the same. Second, closing the loop matters a lot, because a gap shifts the computed centre and drags every distance with it. The dashed ghost circle drawn over your attempt is the ring at your average radius, so it shows exactly where you strayed.

Scoring higher

• Draw big. The wobble is measured relative to the circle's size, and a hand jitters by a roughly fixed amount, so the same shake hurts a large ring less.
• Move fast and from the shoulder. Slow, careful strokes collect more corrections, and corrections are wobble.
• Keep one speed all the way round. Speeding up flattens the arc into an oval, which scores badly.
• Close the loop cleanly. An open circle moves the centre and lowers the whole score.
• Ninety percent is hard. Most people land in the seventies and eighties, and a genuine ninety plus takes practice.

Common questions

How is the percentage worked out?

The game finds the centre of your drawing, measures how far each point of the line is from it, and scores how consistent those distances are. No variation would be 100 percent.

Does a bigger circle score better?

Indirectly. The wobble is measured relative to the circle's size, and a hand shakes by roughly the same amount regardless, so a larger circle hides the same jitter better.

What is the dashed circle?

The perfect ring at your average radius, drawn over your attempt so you can see where you wandered off it.