int led = 11;
int bright = 0;
int fade = 5;

void setup() {
  // put your setup code here, to run once:
  pinMode(led, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  analogWrite(led, bright);
  bright = bright + fade;
  if (bright == 0 || bright == 255)
  {
    fade = - fade;
  }
  delay(100);
}