#include <Servo.h>

Servo myServo;  // create servo object

void setup() {
  myServo.attach(9);  // attach servo to pin D9
}

void loop() {
  // Rotate from 0° to 180°
  for (int angle = 0; angle <= 180; angle += 10) {
    myServo.write(angle);
    delay(500);
  }

  // Rotate back from 180° to 0°
  for (int angle = 180; angle >= 0; angle -= 10) {
    myServo.write(angle);
    delay(500);
  }
}