#include <SoftwareSerial.h> //added a library to use the Serial Monitor

int rxPin = 0; //the recieving pin
int txPin = 1; //the transmitting pin
SoftwareSerial Serial(rxPin, txPin);

int pin_phototransistor = 2; //pin number 2
int value_phototransistor = 0; //give value to phototransistor

void setup() {    
pinMode(rxPin, INPUT); //the rx pin is the input of the communication
pinMode(txPin, OUTPUT); //the tx pin is the output of the communication
pinMode(pin_phototransistor, INPUT); //the phototransistor is an input
Serial.begin(9600); // to enable communication, should correspond to serial monitor 
}

void loop(){
value_phototransistor = analogRead(pin_phototransistor); // read the value of the phototransistor

if (value_phototransistor > 400) { //if it's dark
Serial.println("Good night");
}
else {
Serial.println("Good morning"); //is it's light
}
}