int LDRPin = A0;
int LEDPin = 2;

void setup() {
  // put your setup code here, to run once:
  pinMode(LDRPin, INPUT);
  pinMode(LEDPin, OUTPUT);
}

void loop() {
   // put your main code here, to run repeatedly:
  int LDRPinValue = analogRead(LDRPin);

  if (LDRPinValue < 500) {
    digitalWrite(LEDPin, HIGH);
  } else {
    digitalWrite(LEDPin, LOW);
  }

  delay(1000);
}