What technology is used in the Audi A3 to enhance fuel efficiency?

I'm curious about what makes the Audi A3 such a fuel-efficient car. Can you shed some light on the technology behind it?

The Audi A3 is equipped with a start-stop system that automatically shuts off the engine when the car is idling, reducing fuel consumption.

The A3 also features an aerodynamic design that reduces drag and improves fuel efficiency.

In addition, the A3 uses a regenerative braking system, which captures and stores energy that is normally lost during braking, further improving fuel economy.