Hi, I am helping my children with a computer game based on Logic and Reasoning. The player has to solve different puzzles as the game progresses. I am struggling with a matching puzzle where the player has to form a string of the game characters based on their traits. Please see the attached file for a snapshot of the puzzle. I am not sure how I should approach such a problem. I also wish to know the branch of Mathematics that studies this kind of problems. Brief background. The characters in the game are called Zoombinis, with each of them having four special characteristics : hair, eyes, nose, and foot. Based on 4/5 variations of the each of the charactristics, the game randomly produces zoombinis. The player has to guide around 16 zoombinis at a time through various puzzles. At the above mentioned matching puzzle, the game produces a string of holes (where one zoombini can be placed) . Between two holes a picture of one of the 4 characteristics is shown. The two zoombinis on the either side of a picture have to have the same trait. For example, if there is an eye picture between two holes, then the zoombinis on the either side of that picture have to have similar types of eyes; both of them can have sleepy eyes, or wide-open eyes, or eyes covered with glasses. Thanks, MG.