Complex sentence: Before the start of "Kung Fu Panda 2", Shen was the prince of Gongmen City who became interested in the power of gunpowder, wondering if it and the technology behind fireworks could be used for warfare.
Split into simpler sentences: Before the start of "Kung Fu Panda 2", Shen was the prince of Gongmen City. Shen became interested in the power of gunpowder, wondering if it and the technology behind fireworks could be used for warfare.