The History of Pattern Rows
Rows of repeating signs are as old as pottery and weaving - and continuing them is a favourite task in school books and tests.
Borders and Bands
Bands of repeated signs run around pots, along the edges of woven cloth and over the walls of old buildings, in many cultures and at many times. Whoever weaves or paints such a band has to know what comes next.
In School and in Tests
Carrying a row on is a classic exercise in children's workbooks and in intelligence tests. John C. Raven, for example, published his Progressive Matrices in the late 1930s, in which the missing piece of a pattern has to be found.
How PaperGames Makes Each Row
Every row is built from a short group of symbols that is shown at least twice. The program then checks that no other group would put a different symbol in the empty place, so each row has exactly one right answer.