How does the game detect corners in my drawing?

The algorithm simplifies your drawn path, then measures the local angle change at each point. The four points with the sharpest angle changes (most acute local bends) become your corners. If your path has extra wobbles or you've drawn more than four apparent corners, the scoring may be off — draw crisply.

Why does my square look right on screen but score poorly?

The score is unforgiving about two things: sides that differ in length by more than ~10% and corners that deviate from 90° by more than ~15°. Both errors compound — a shape that's square-looking but slightly rotated can have all four corners reading as 85–95°, which still costs points.

What is the difference between drawing a perfect square and a perfect circle?

A circle is scored on smoothness and constant curvature — a fluid, continuous motion helps. A square rewards sharp discontinuities (corners) and straight segments. They use completely different motor programs, and people who excel at circles often struggle with squares and vice versa.

Can You Draw a Perfect Square?

Drawing a perfect square freehand sounds simple — four equal sides, four right angles — but the geometry is surprisingly demanding. This test asks you to draw a square in one continuous motion and scores you on two things: how equal the four sides are and how close each corner is to 90°. The game detects your four corners automatically using a curvature algorithm, then computes the composite error. Most people's first attempt looks more like a squashed trapezoid than a square.

How to Play

Press Start and draw a closed quadrilateral in one continuous motion — try to return to your starting point.
The game simplifies your path and automatically finds the four most prominent corners.
Press Submit. A blue dashed ideal square is overlaid at the calculated centre and average side length.
Your score reflects a weighted composite of side-length variance and corner-angle deviation from 90°.
Close the shape cleanly — the algorithm needs a clear loop to identify all four corners reliably.

Why It's Hard

A square has two independent constraints: equal sides and right angles. Satisfying both simultaneously without a ruler requires holding a precise mental model of the shape while executing the motor program. The difficulty is compounded by the fact that your natural wrist arc traces curves, not straight lines — each side wants to bow inward. You also need to change direction sharply at each corner without overshooting, which requires an abrupt motor correction mid-stroke.

Tips

1Slow down at each corner: a clean 90° turn scores far more than a fast wobbly one.
2Draw in a raster order — top side left-to-right, down the right side, bottom right-to-left, then close up the left — this aligns with natural arm movements.
3Mentally divide the canvas into thirds and aim for your corners at the inner grid points for a well-proportioned square.

FAQ

How does the game detect corners in my drawing?: The algorithm simplifies your drawn path, then measures the local angle change at each point. The four points with the sharpest angle changes (most acute local bends) become your corners. If your path has extra wobbles or you've drawn more than four apparent corners, the scoring may be off — draw crisply.
Why does my square look right on screen but score poorly?: The score is unforgiving about two things: sides that differ in length by more than ~10% and corners that deviate from 90° by more than ~15°. Both errors compound — a shape that's square-looking but slightly rotated can have all four corners reading as 85–95°, which still costs points.
What is the difference between drawing a perfect square and a perfect circle?: A circle is scored on smoothness and constant curvature — a fluid, continuous motion helps. A square rewards sharp discontinuities (corners) and straight segments. They use completely different motor programs, and people who excel at circles often struggle with squares and vice versa.

Built by

Ethan R. Caldwell

Game Developer · Wilmington, DE

Designed Can You Draw a Perfect Square? and 46 other browser puzzles. Game developer based in Wilmington, Delaware. Hardcore puzzle gamer at heart — obsessed with logic puzzles, sokoban-style mechanics, and physics-based brain teasers. Off the clock, unwinds with ARPGs, RPGs and JRPGs.

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