Chess, Arquebus, Printing Press, Mainspring

Chess: A chess board has white and brown squares. There are 64 squares. Each player gets 16 pieces. Each player gets 8 pawns which represent foot soldiers. Knights are the main attackers. It quickly spread throughout Europe.

Arquebus: It made warfare cheaper. 25% of the King of Hungary's army carried an arquebus. A series of inventions improved a hand cannon.

Printing Press: The printing press is the single most important invention of the past 1,000 years. Books could now be printed faster and cheaper. The Bible was the first book to be printed.

Mainspring: The mainspring was first used in locks in the 1400s. Its use went into decline in the 20th century as electronics began taking over.