Star fort of the time was the state of the art in fortifications. Direct response to the evolution of firearms and artillery. Curtain walls were no longer enough protection against cannon, and they had to be earth-berm backed walls. The star configuration gave interlocking fields of fire, allowing one bastion to prevent being overtopped by infantry to the bastions on either side of it. Remember that when someone wants to ban guns, they are literally trying to ban a 16th century technology.