int ledPin = 2;      // the number of the LED pin
int brightness = 0;  // how bright the LED is
int fadeAmount = 25; // how many points to fade the LED by

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  analogWrite(ledPin, brightness);
  
  brightness = brightness + fadeAmount;
  
  if (brightness <= 0 || brightness >= 255) {
    fadeAmount = -fadeAmount;
  }
  
  delay(30); // wait for 30 milliseconds to see the dimming effect
}