Red Alert 3 retains the core real-time strategy mechanics of the Command & Conquer series. Warring factions harvest resources using vulnerable collectors and use those resources to construct military bases and forces on-site. Structures form a shallow but wide tech tree with a variety of units and elusive superweapons. Weapon types are specialized to the point where a rifleman can withstand direct hits from an anti-tank cannon. Red Alert 3's major refinements are the addition of the Empire of the Rising Sun to the factions of the sub-series, a co-operative campaign, and expanded naval warfare.