[JohnC]

We use Left(int) and Right(int)

void Left(int speed) {
  pwm01 = speed;
  
  if(pwm01 > 254) {
    pwm01 = 254;
  } else if(pwm01 < 1) {
    pwm01 = 1;
  }
}

And the right one assigns 254-speed. Just yet another form of abstraction