Puzzle No. 030
Picarats: 30


Have you heard of one-line puzzles? The idea is to place your pen to paper and draw a shape without lifting your pen from the pad or retracting any part of the line. You can, however, cross lines.

Now that you're familiar with the concept, look at the four pictures below. One of them cannot be drawn  with one line.

Which one is it?














Hint One: Each picture should be composed of lines that meet at different points.

With these pictures, if you find a single line that runs out beyond the others, you know you have to start your drawing there.

Try tracing the answer out yourself.

Hint Two: Some points may be the convergence point for several lines. You need to think hard about which line to take in and out of the point in order to make the sketches work.

If your pen is entering a point formed by an even number of lines, you will always be able to leave the point via another line.

Hint Three: One of the familiar objects below can't be drawn as a one-line puzzle.

You'd be surprised by how easily some of the more complicated pictures can be drawn in one stroke.

Solution:













Very nice! There's actually a very east way to tell whether or not a given picture has been drawn in one stroke. This method will be revealed to you after you solve one more of these riddles.