The Accidental Alchemist. Survival through the Ages, #7

Waking up in a dense bamboo forest in 10th-century China, 15-year-old Robert stumbles upon a secret workshop where Song Dynasty scholars are accidentally creating "The Fire Drug"-the world's first black powder. While the alchemists struggle to control the volatile substance, Robert uses his modern "mechanic's brain" and knowledge of physics to show them how to use bamboo tubes to direct the energy.
He effectively invents the first "fire arrows" and spinning ground fireworks, turning a dangerous accident into a controlled wonder. The situation turns deadly when the local military discovers the breakthrough and demands Robert turn his "celebration powder" into a weapon of war. Caught between the peaceful inventors and a ruthless general, Robert must use his tactical hunting skills and his newly engineered pyrotechnics to stage a massive, distracting "Festival of Light" escape.
As he outmaneuvers the soldiers under a sky of primitive fireworks, he tracks the shimmering "glitch" through the smoke, plunging through it to wake up safely in his own bed in 2020.