I guarantee you will enjoy this website...and it will both puzzle and frustrate you. Yet, I expect you will suggest it to others.
First, some rules, etc. The game Eyeballing shows you a series of geometrical figures that need slight adjustments to make them exact. In most figures, a square represents the point that you need to use the mouse to move via your "eyeballing." Release the mouse, and the computer evaluates your move, and the "correct" geometry is shown in green...and you are being timed!
In a game, you are presented with each challenge three times. The table on the right keeps track of how you did on each challenge each time.
At the end of the game, the computer determines your average error (the lower the better). Also, the computer maintains a "best scores" table, one for all visitors and one for just your computer.
Enough...get on with playing Eyeballing.
The game is provided by the website Woodgears...An Engineer's Approach to Woodworking, which is maintained by Matthias Wandel. You may want to visit his personal website as well, as he dabbles in mathematical art (i.e. parametric transcendental formula art), weird marble machines, Lego machines, and insane contraptions.
Note: The game Eyeballing was used as part of a research project by David Rockoff and Heike Hofmann. Their focus was on relationships of a person's visual eyeballing ability and communication via statistical graphics. The summary of their research can be found in the journal Chance (Vol. 24#1, 2011, pp. 35-45). Find it, as it is an interesting read!