Lines, a river, two palaces
Pieces sit on the intersections of 9 vertical files (a–i) and 10 horizontal ranks (0–9); Red sits at the bottom, and ranks count up from Red's side. The river cuts the board in half between ranks 4 and 5: elephants may never cross it, and a soldier that does cross earns the sideways step. The two river banks — the fourth and fifth ranks — are the busiest lanes on the board; later chapters are built on the chariots and cannons that patrol them. Each side also hides a 3×3 palace marked with diagonals: the general and his advisors never leave it. Take the board for a spin: push a soldier.
Solve the challenge to finish this lesson.