int LDR_pin = A0;       // initializing pin 4 as the sensor output pin
int buzzer_pin = 3;             // initializing pin 8 as the buzzer pin
int led_pin = 13;                // initializing the pin 2 as the led pin
 
 int LDRState = 0;           // state of sensor
  
   
   void setup()
   {
     pinMode(led_pin, OUTPUT);             // declaring led pin as output pin
       pinMode(LDR_pin, INPUT);     // declaring sensor pin as input pin for  Arduino
         pinMode(buzzer_pin, OUTPUT);          // declaring buzzer pin as output pin
           Serial.begin(9600);                   // setting baud rate at 9600
           }
            
             
             void loop()
             {
               LDRState = analogRead(LDR_pin);          // reading from the sensor
                 Serial.println(LDRState);
                       
                          if (LDRState >= 8 && LDRState <= 900 )                               // applying condition
                            {
                                Serial.println("It is dark now");
                                    digitalWrite(led_pin, HIGH);                      // if state is high, then turn high the led
                                       playMelody();                                   // play a melody on the buzzer
                                           delay(1000);
                                             }
                                               else
                                                 {
                                                     Serial.println("It is still daytime");
                                                         digitalWrite(led_pin, LOW);                       // otherwise turn it low
                                                            // noTone(buzzer_pin);  
                                                                delay(1000);// stop playing any tone
                                                                  }
                                                                  }
                                                                   
                                                                    
                                                                    void playMelody()
                                                                    {
                                                                      // Play a simple melody: C4, E4, G4, C5
                                                                        tone(buzzer_pin, 262, 200);             // C4
                                                                          delay(200);
                                                                            tone(buzzer_pin, 330, 200);             // E4
                                                                              delay(200);
                                                                                tone(buzzer_pin, 392, 200);             // G4
                                                                                  delay(200);
                                                                                    tone(buzzer_pin, 523, 200);             // C5
                                                                                      delay(200);
                                                                                      }