// Pin number for the LED
const int ledPin = 9;

void setup() {
  // Set pin 9 as an output
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // Gradually increase brightness
  for (int brightness = 0; brightness <= 255; brightness++) {
    analogWrite(ledPin, brightness); // Set LED brightness
    delay(10); // Small delay for a smooth transition
  }

  // Gradually decrease brightness
  for (int brightness = 255; brightness >= 0; brightness--) {
    analogWrite(ledPin, brightness); // Set LED brightness
    delay(10); // Small delay for a smooth transition
  }
}