What is a good deviation score for a straight line test?

Under 5 px average deviation is excellent for a typical screen. Between 5–10 px is average. Above 15 px usually means the line has a visible curve or wobble. The scoring function uses a 28 px threshold as the zero-score boundary.

Why are diagonal lines harder than horizontal or vertical ones?

Your motor system is optimised for the cardinal axes — horizontal strokes follow natural forearm extension, and vertical strokes follow elbow flex/extension. Diagonal lines at arbitrary angles require a coordinated blend of both, which the brain handles less efficiently and with more variance.

Can practice actually improve your ability to draw straight lines?

Yes. Draughtsmen and illustrators practice "ghosting" — rehearsing the stroke path in the air above the surface before committing. This pre-programs the motor sequence and typically reduces deviation by 30–50% compared to cold attempts. Try it: hover your finger/cursor along the intended path twice before drawing.

Can You Draw a Perfect Straight Line? — Straight Line Test — Play Free

The straight line test strips drawing down to its simplest form: two points appear on screen, labelled A and B, and you draw freehand from one to the other. No ruler. No guides. Your path is scored on deviation — the average pixel distance between each point you drew and the true mathematical line from A to B. It sounds trivially easy, but the moment the line is at an unusual angle your hand has no natural movement to fall back on, and wobble creeps in fast.

How to Play

Press Start. Points A and B appear at a random angle and length across the canvas.
Click and drag (or touch and drag) from near point A toward point B in a single stroke.
Release when you reach point B. Press Submit to score.
After scoring, the ideal straight line is shown in blue dashed overlay alongside your red path.
The deviation score is the average pixel distance across all your drawn points from the A-to-B line.

Why It's Hard

Truly straight freehand lines require your arm to execute a ballistic movement — a single, committed stroke with no mid-course correction. Short lines are easy because your wrist can bridge the gap in one flick. Long lines are hard because your wrist rotation introduces a natural arc: the radius of your wrist joint means any wrist-only stroke traces a slight curve. Diagonal lines at 30–60° are hardest, as they fall outside the natural horizontal/vertical planes your motor system practices most.

Tips

1Lock your elbow and use your shoulder as the pivot for long lines — wrist-only strokes will arc.
2Move fast and commit: a single confident stroke deviates less than a slow, hesitant one where you try to self-correct.
3Near-vertical lines are easiest for right-handers; near-horizontal lines are easiest for left-handers — play to your natural movement axis.

FAQ

What is a good deviation score for a straight line test?: Under 5 px average deviation is excellent for a typical screen. Between 5–10 px is average. Above 15 px usually means the line has a visible curve or wobble. The scoring function uses a 28 px threshold as the zero-score boundary.
Why are diagonal lines harder than horizontal or vertical ones?: Your motor system is optimised for the cardinal axes — horizontal strokes follow natural forearm extension, and vertical strokes follow elbow flex/extension. Diagonal lines at arbitrary angles require a coordinated blend of both, which the brain handles less efficiently and with more variance.
Can practice actually improve your ability to draw straight lines?: Yes. Draughtsmen and illustrators practice "ghosting" — rehearsing the stroke path in the air above the surface before committing. This pre-programs the motor sequence and typically reduces deviation by 30–50% compared to cold attempts. Try it: hover your finger/cursor along the intended path twice before drawing.

Built by

Ethan R. Caldwell

Game Developer · Wilmington, DE

Designed Can You Draw a Perfect Straight Line? 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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