Engine tutorial producer Repairman22 posted this informative 3D animation on YouTube illustrating how a 2CV engine is constructed and operates.
Not only does he show its brilliance, he also discusses the superiority of the 2-cylinder 2CV engine over the 4-cylinder Volkswagen Beetle engine. It’s what most 2CV owners who have some familiarity with the Volkswagen Beetles already know, but whether you do or not, his explanation is well worth watching: