A puzzle is a mental challenge, usually suitable for one person to solve alone.
Puzzles encompass a wide variety of mental challenges, from crosswords to conundrums to jigsaws.
They can be trivially easy, frustratingly hard, or anywhere in between. The greatest pleasure comes from those where the solution involves some novel way of thinking, or looking at the problem from an unexpected viewpoint. Only 1s 2s and 3s allowed. Answer Two cars are 120 miles from each other on a straight road. At the instant they set off, a bird leaves one car, flying towards the other at 60 mph.