A Poor Nobody with AI in His Head Outwits Immortals and Unifies the World

Tang Dynasty, Build a Steam Engine: I Want the Technology, Not a System That Hands Out Finished Products

Technology-focused, with lots of knowledge, and preferably plenty of text.

Any Stories About Transmigrating to Ancient Times, Where a System and Modern Technology Outclass the Ancients?

Any Stories Where the Protagonist Transmigrates to Ancient Times and Uses Modern Knowledge to Invent All Kinds of Things?

Ideally, it should include inventions such as fireworks.

Novels About Returning to Ancient Times and Developing Technology Like Crazy

The protagonist either transmigrates into the past or gains the ability to travel back and forth to ancient times, helping advance technology there and shocking the people of the era. Preferably a real historical dynasty, but a fictional one is fine too.