Why is the Audi A2 considered one of the most advanced cars in its time?

I am trying to understand the features and technology that made the Audi A2 stand out in its time. Can someone explain what sets it apart from other cars of its era?

The Audi A2 was a pioneer in lightweight vehicle construction, using aluminum in its body to reduce weight and improve fuel efficiency. It also had advanced features such as start-stop technology and regenerative braking, making it ahead of its time.