int photoCellPin = A0;

// Create a variable to hold the light reading
int photoCellReading = 0;

// Define a pin we'll place an LED on
int ledPin = D2;

// Create a variable to store the LED brightness.
int ledBrightness = 0;

void setup() {
    
pinMode(ledPin, OUTPUT);

 // Create a cloud variable of type integer
  // called 'light' mapped to photoCellReading
  Particle.variable("light", &photoCellReading, INT);


}

void loop() {
    
// Use analogRead to read the photo cell reading
  // This gives us a value from 0 to 4095
  photoCellReading = analogRead(photoCellPin);

  // Map this value into the PWM range (0-255)
  // and store as the led brightness
  ledBrightness = map(photoCellReading, 0, 4095, 0, 255);

  // fade the LED to the desired brightness
  analogWrite(ledPin, ledBrightness);

  // wait 1/10th of a second and then loop
  delay(100);

}