“Many public-school children seem to know only two dates—1492 and 4th of July; and as a rule they don’t know what happened on either occasion,” lamented American writer and wit Samuel L. Clemens (alias Mark Twain), whose star went out 100 years ago this April. Perennially short on cash and obstinately fascinated by inventions without promise, Twain hatched a scheme for a children’s history game in 1883 that he hoped would net millions. Beginning that year, Twain began to routinely push aside his nearly complete manuscript of Adventures of Huckleberry Finn to labor over the game, which he patented in 1885 as “Mark Twain’s Memory-Builder: A Game for Acquiring and Retaining All Sorts of FACTS and DATES.”