int btnHigh = 3;
int btnLow = 2;
int ledPin = 9;

int brillo = 255;

void setup() {
  // put your setup code here, to run once:
  pinMode(btnHigh, INPUT_PULLUP);
  pinMode(btnLow, INPUT_PULLUP);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  if(digitalRead(btnHigh) == LOW){
    incrementar();
  }

  if(digitalRead(btnLow) == LOW){
    decrementar();
  }

  analogWrite(ledPin, brillo);
  delay(300);
}

void incrementar(){
  if(brillo >= 255){
    flashLED();
  }else{
    brillo += 51;
  }
}

void decrementar(){
  if(brillo <= 0){
    flashLED();
  }else{
    brillo -= 51;
  }
}

void flashLED() {
  for (int i = 0; i < 2; i++) {
    digitalWrite(ledPin, HIGH);
    delay(300);
    digitalWrite(ledPin, LOW);
    delay(300);
  }
}