A* pathfinding
How the original engine finds a ground unit's path — the A* search, its movement-cost weights, tie-break rules, termination caps, and the corner-smoothing that shapes the final route.
Cell occupation and sub-cell spots
How each cell records what stands on it — ground and bridge occupancy layers, the four infantry sub-cell spots, the owner stamp, and the cell-entry verdict pathfinding shares. Verified: Tiberian Sun, Red Alert 2, and Yuri's Revenge.
Nearest-valid-spot placement (NearByLocation)
How the original engine finds the nearest cell that satisfies a placement filter chain — a square-ring scan with a fixed candidate order, cap, and tie-break. Verified: Tiberian Sun, Red Alert 2, Yuri's Revenge.