int photoCellPin =A0;
int photoCellReading=0;
int ledPin=D2;
int ledBrightness=0;

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

Particle.variable("light",&photoCellReading, INT);

}

void loop() {
//analogRead reads the photocell, and gives a value from 0 to 4095
photoCellReading =analogRead (photoCellPin);

//We want to map this value into the PWM range of 0-255
ledBrightness =map(photoCellReading, 3000,4095,0,255);

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

//waits and then loops
delay(100);
}