Why is the fuel economy of the Audi A2 so impressive?

I've been researching cars and I keep seeing the Audi A2 listed as having exceptional fuel economy. What makes it stand out from other cars in its class?

The Audi A2 utilizes lightweight materials and aerodynamic design to improve its fuel efficiency. In fact, it was one of the first production cars to incorporate an aluminum body.

Its efficient and powerful TDI diesel engine also contributes to its impressive fuel economy. Even with its smaller size, the Audi A2 still delivers a comfortable and enjoyable driving experience.