Programmer Lin Yi accidentally traveled through the Southern Song Dynasty with the soul of "Infrastructure System" and became a demoted ninth-rank official. He relied on the system to exchange cement, improved seeds and firearms, starting from the reconstruction of dilapidated county towns, building roads, mining, and training troops to fight the enemy. When the Mongolian cavalry went south, they had built industrial castles one after another in the troubled times, allowing the cultural spark of the Song Dynasty to rekindle in the steam and gunpowder smoke.
