The Think-a-Dot, produced by E.S.R., Inc. in early 1966 and based on a game concept by Joseph Weisbecker, is a computer-based puzzle theory toy that demonstrated automata theory. It is a plastic toy with three holes on top through which a ball is dropped, triggering a disk in the front of the game to turn either blue or yellow. These flipped disks would, in turn, determine the paths of subsequent balls. The game was immensely successful for both E.S.R. and Weisbecker. It was featured three times in Mathematics Magazine, which praised “the richness of [the game’s] mathematical theory that has been built on so modest a foundation,” and whose final article about the game appeared in 1979, suggesting that it was still at least moderately popular more than a decade after it was first manufactured. It was also used in educational therapy, and Weisbecker wrote to game designer Sid Sackson in 1969 that it was being used in therapy for children with left-right discrimination problems. Neither its educational usefulness nor its entertainment value has waned in the 21st century, and modern-day players can play a simulated version made with MIT Media Lab’s Scratch.