Mini Games
Draw a Perfect Circle
Draw a perfect circle in one stroke. The Kasa circle-fitting algorithm scores your attempt from 0 to 100%.
How to play
- Press Start, then draw one circle in a single stroke — any direction works.
- Bring the end back to where you started; a gap or a missing arc costs points.
- Let go to see your 0–100% score and grade.
My Best
---
95% or higher earns Hand of God.
Ranking
| Rank | Nickname | Score |
|---|---|---|
| Rank | Nickname | Score |
|---|---|---|
- |  You | - |
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Draw a Perfect Circle is a one-stroke drawing test: press down on the canvas, draw a single loop with your mouse, finger or stylus, and let go. The game fits the best possible circle through every point you drew using the Kasa least-squares method, then gives you an accuracy score from 0 to 100% with two decimals. Roundness — how evenly your line stays at the same distance from the fitted centre — makes up 70% of the score, closing the loop makes up 30%, and the total drops if part of the circle is missing.
There is no timer and direction doesn't matter, so you can take it slowly. Pivot from the wrist or elbow instead of the fingertips, keep an even pace all the way round, and finish exactly where you started. The dashed circle on the empty canvas shows a comfortable size; strokes that are too short or too small are not scored and simply let you draw again.
95% or more earns Hand of God, 85% Artist, 70% Solid and 50% Almost a circle. Your result goes on all-time, daily, weekly and monthly leaderboards, and the share card includes a link that challenges friends to beat your exact score. Vasari tells how Giotto convinced a papal envoy of his skill with nothing but a freehand red circle — see how close your hand can get.
Frequently Asked Questions
Q. How is the circle score calculated?
A. It is roundness (70%) plus closure (30%), multiplied by how completely the stroke goes around. The game fits a best-fit circle with the Kasa least-squares method; roundness is 1 minus the spread of your distances from its centre divided by the average radius, closure compares the start–end gap with the diameter, and any missing arc wider than about 17° lowers the total.
Q. What score do I need for each grade?
A. Hand of God (S) needs 95% or more, Artist (A) 85%, Solid (B) 70% and Almost a circle (C) 50%. Anything below 50% is graded D.
Q. Why didn't my circle get a score?
A. The stroke was too short or too small. A result needs at least 12 sampled points and a fitted radius of at least 20 pixels; otherwise the canvas clears so you can try again. Drawing about the size of the dashed guide avoids this.
Q. Do drawing speed or direction affect the score?
A. No. There is no time limit, and clockwise and counter-clockwise loops are scored the same way — only the final shape counts, so drawing slowly usually helps.
Q. Is there a leaderboard?
A. Yes. Every scored attempt is submitted to all-time, daily, weekly and monthly rankings, and the share button creates an image of your circle plus a challenge link with your score.