Jigsaw puzzles
To us puzzles are just games to pass the time away. They satisfy an innate desire to accomplish something. Jigsaw puzzles are challenging because of the myriad pieces that need to be pieced together to complete a picture. The harder the puzzle the better satisfaction we get when it is completely done. It can also be very frustrating when cannot find the perfect location for an itinerant piece.
To scientists, jigsaw puzzles are tools that help the mental state of some patients. They say that successfully piecing a puzzle together, even just placing one piece successfully, encourages the production of dopamine, a brain chemical that improves learning and memory. Jigsaw puzzles create literal connections between the right and left brain, as well as individual brain cells, which increases the ability to learn. That is the scientific explanation of why Sudoku and Christian puzzles exercise the brain.