Five rounds of guessing how long a bar is. You get one bar you already know the length of, and that is the only help there is.
One bar is labelled. Hold it in your eye, then look at the mystery one and ask how many of the first would fit along it. That is measuring by comparison, and it is what everybody does before they reach for a ruler.
Type a number and press it. Do not shuffle it about after you have decided. The point is to find out what your eye actually does, and you cannot find that out if you keep editing the answer.
Most people are wrong in the same direction every time. If you are always under, you will be always under on a real thing too. Knowing which way you lean is worth more than the score.
Every number on our drawings is a millimetre, and the first skill anybody on a bench learns is guessing one before reaching for the ruler. The brown bar is 50 mm. Guess the orange one. Inside 3 mm counts, because that is what a tolerance is: not right, close enough on purpose.
Both bars share one scale on screen, so it works at any zoom on any display. Your best score is kept on this device and goes nowhere else. There is nothing to sign in to and nothing to send us.
That is the end of this one
The word for what you just did is tolerance.
Inside three millimetres counts as a hit here, and that three is the whole lesson. Nothing ever comes out exactly on the number, so somebody has to decide in advance how far off is still fine. That decision is called tolerance, it gets written on the drawing before anything is made, and deciding it afterwards is how everybody cheats.
Where to go now