Why do Audi A2 models have such low drag coefficients?

I noticed that Audi's A2 models have impressively low drag coefficients, sometimes even lower than some electric cars. Can anyone explain why this is the case and what specific design features contribute to this?

Audi A2 models have low drag coefficients due to their aerodynamic design, which minimizes wind resistance. Some key design features that contribute to this are its rounded shape, smooth underbody, and adjustable roof spoiler.