void setup() {
  // put your setup code here, to run once:

}

void loop() {
  for (int i=0; i <= 255; i++){ 
  

   digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(250);                       // wait for a second
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
  delay(250);          
}
}