Technology advanced significantly during this period. Shu chancellor Zhuge Liang invented the wooden ox, suggested to be an early form of the wheelbarrow, and improved on the repeating crossbow. Wei mechanical engineer Ma Jun is considered by many to be the equal of his predecessor Zhang Heng. He invented a hydraulic-powered, mechanical puppet theatre designed for Emperor Ming of Wei, square-pallet chain pumps for irrigation of gardens in Luoyang, and the ingenious design of the south-pointing chariot, a non-magnetic directional compass operated by differential gears.