What is the main ocean of this passage: Fireworks are a class of explosive pyrotechnic devices used for aesthetic, cultural, and religious purposes. The most common use of a firework is as part of a fireworks display. A fireworks event (also called a fireworks show or pyrotechnics) is a display of the effects produced by firework devices. Fireworks competitions are also regularly held at a number of places. Fireworks take many forms to produce the four primary effects: noise, light, smoke, and floating materials (confetti, for example). They may be designed to burn with flames and sparks of many colors, typically red, orange, yellow, green, blue, purple, and silver. Displays are common throughout the world and are the focal point of many cultural and religious celebrations. The earliest documentation of fireworks dates back to 7th-century China, where they were invented. The fireworks were used to accompany many festivities. The use of fireworks is a part of the culture of China and had its origin there; eventually it spread to other cultures and societies. The art and science of firework-making has developed into an independent profession. In China, pyrotechnicians were respected for their knowledge of complex techniques in mounting fireworks displays.

During the Song Dynasty (960–1279), many of the common people could purchase various kinds of fireworks from market vendors, and grand displays of fireworks were also known to be held. In 1110, a large fireworks display was included in a martial demonstration held to entertain Emperor Huizong of Song (r. 1100–1125) and his court. A record from 1264 states that a rocket-propelled firework went off near the Empress Dowager Gong Sheng and startled her during a feast held in her honor by her son Emperor Lizong of Song (r. 1224–1264). HELP ASAP!!! i cant figure out the main idea