Why do Audi A2s have aluminum frames instead of steel?

I've noticed that the Audi A2 has an all-aluminum space frame, rather than a steel frame like most other cars. Is there a specific reason for this design choice and how does it impact the car's performance and durability?

Having an aluminum frame reduces the weight of the car, improving fuel efficiency and performance. It also allows for better weight distribution and handling. However, it may be more susceptible to damage in a collision compared to a steel frame.