const int pinBt1 = 2;
const int pinBt2 = 3;
const int pinLED = 9;

void setup() {
  pinMode(pinBt1, INPUT);
  pinMode(pinBt2, INPUT);
  pinMode(pinLED, OUTPUT);
  digitalWrite(pinBt1, HIGH);
  digitalWrite(pinBt2, HIGH);
}

int cahaya = 0;

void loop() {
  if (digitalRead(pinBt1) == LOW){
    cahaya++;
  } else if (digitalRead(pinBt2) == LOW){
    cahaya--;
  }
  cahaya = constrain(cahaya, 0, 255);
  analogWrite(pinLED, cahaya);
  delay(20);
}