Quake 2's base mechanics served as a scaffolding for this - a set of fun, smart, modern levels with themes, escalating tension, incredible level design, and great environment art. Something of this scope can only be achieved in the modern era by looking backwards to what made games like Half-Life 2 and the modern Dooms great. The only thing holding it back is Quake 2's gunplay and spongy enemies, but Call of the Machine easily earns a place at the top of the great modern boomer shooter campaigns. Easy to recommend over the base Quake 2 campaign.