Eyeball

How good is human visual estimation?

Your visual system is excellent at relative comparison and surprisingly poor at absolute judgement. You can instantly tell which of two lines is longer, but asking you to find an exact midpoint or a true right angle exposes consistent biases. Most people cut a bar slightly off centre, and most people make a square that is a little too wide. Eyeball turns those biases into a score.

The biases this game reveals

Bisection bias means people tend to place a midpoint shifted toward one side, often the side their dominant eye favours. The horizontal-vertical illusion makes vertical extents look longer than equal horizontal ones, which is why squares come out wide. Knowing these tendencies lets you correct for them. If you always cut left of centre, nudge right on purpose.

Practice changes your accuracy

Visual estimation improves fast with feedback. Each round shows your guess against the target, and that side-by-side reveal is the training signal. Play the daily puzzle, see your error direction, and adjust. Within a handful of sessions most players cut their average error in half.