#define LDR_PIN 2
#define LED 4

void setup() {
  Serial.begin(115200);
  Serial.println("LDR");
  pinMode(LED, OUTPUT);
  pinMode(LDR_PIN, INPUT);
}

void loop() {
  if (digitalRead(LDR_PIN)== LOW) {
    digitalWrite(LED, HIGH);
  } else {
    digitalWrite(LED, LOW);
  }
  delay(250);
}