The reunification of China was finally completed in 221 BC by Wang Cheng. He immediately decided to come up with a new title: 'huangdi', which meant 'August God', or as we would say, Emperor. He then took upon himself the name Shihuangdi, 'First Emperor'. Wang became the title used for princes and also for kings of other lands. After this time emperors were generally known by their 'temple names', ie the names given to them after death which described their accomplishments. These tended to end either with 'di', which came to mean emperor, or 'tsu', which meant founder of a new dynasty. Shihuangdi was one of the most ruthless and brutal emperors in Chinese history. He was responsible for the building of the Great Wall and expanded Chinese control to the South China Sea. He was buried with the famous Chinese terracotta warriors near Sian. It was during the Ch'in Dynasty that the world's first compass was constructed in China, by balancing a piece of lodestone on a copper plate.