The History of Shadow Pictures
Shadows have been traced, cut out and played with for centuries - matching a shadow to its object is a small exercise in looking closely.
Silhouettes and Shadow Play
Cutting a shape out of black paper is called a silhouette, a word that became common in 18th-century France for such portraits. Shadow plays, in which flat figures are held in front of a light, are even older and are known from Asia and from Europe.
Looking Closely
Workbooks for children often ask which shadow belongs to which picture. To answer, you compare outlines and notice small differences: where the tail is, which way something faces, whether it stands on its head.
How PaperGames Makes Each Round
All twenty pictures are drawn for PaperGames. A shadow is the same drawing in solid black, so it always fits its picture exactly. The wrong shadows come from other drawings or from the same drawing turned, and the program makes sure that no two shadows in a round are the same.