const int ldrPin = A0;
 const int ledPin = 9; 
 const int threshold = 500; 
 void setup() {
 pinMode(ledPin, OUTPUT);
 Serial.begin(9600);
 }
 void loop() {
 int ldrValue = analogRead(ldrPin);
 Serial.print("LDR Value: "); 
 Serial.println(ldrValue); 
 if (ldrValue < threshold) { 
 digitalWrite(ledPin, HIGH);
 } else {
 digitalWrite(ledPin, LOW);
} delay(100); 
 }