KOEN

Optical Center Test

TEST · OPTICAL CENTER

How good is your eye? Ten tasks, from finding the center of a box to making a right angle, measure how many pixels and degrees off you are. A fun visual precision test.

ROUND 01/10
PX

Center of the box

Place the dot exactly in the middle of the rectangle.

Drag anywhere to move it relatively
HOW TO

How to use

  1. Ten eyeballing tasks appear in random order: centers, midpoints, levels, right angles, parallels and more.
  2. Drag the dot, line or arm into place. With a mouse, click to jump there; on touch, drag anywhere and it moves the same way.
  3. Use the arrow keys for 1px or 0.1° nudges (Shift for 10px or 1°), or turn on Precision mode with F.
  4. Press Confirm (or Enter) to see your error and the correct answer, then move on. After ten rounds you get your eye score and grade.
PAIRS WELL WITH

Pairs well with

FAQ

FAQ

What tasks are included?

Five position tasks (center of a box, midpoint between two shapes, center of a circle, one-third point and making a square) and five angle tasks (level, plumb, right angle, parallel lines and bisecting an angle). Each appears once per game in random order.

How is “Your eye is off by n px” calculated?

It's the average error across the five position tasks, measured on a 600×450 reference board so results are comparable on any screen size, phone included. Angle tasks are shown separately as an average error in degrees.

How do the score and grades work?

Each task scores 100 for zero error, dropping quickly past about 12 px for position or 3.5° for angles. A 10-task average of 92+ is Pixel Perfect, 80+ Eagle Eye, 65+ Designer's Eye and 45+ Average Eye.

Where is my best score saved?

Your highest-scoring run (score, px and degrees) is saved only in this browser. It isn't sent to a server and won't carry over to other devices or private windows.