Bongard problems are a type of puzzle invented by Mikhail Moiseevich Bongard, a Russian computer scientist who lived from 1924-1971. A Bongard puzzle presents two sets of six diagrams each, and the solver's goal is to determine what factor distinguishes the two sets. You can see a great many of these puzzles, including Bongard's original 100, here.

Some time ago I decided to make papercraft Bongard problems as presents for friends and family. Here are some photographs of each card, which should be high resolution enough for you to solve from: