int sensorPin = A0;
int sensorReading = 0;
int ledPin = D1;
int ledBrightness = 0;

void setup() {
  pinMode(ledPin, OUTPUT);
  Particle.variable("light", &sensorReading, INT);
  Particle.variable("brightness", &ledBrightness, INT);
}

void loop() {
  sensorReading = analogRead(sensorPin);
  Serial.println(sensorReading); 
  if (sensorReading < 3700) {
    ledBrightness = 255;
  } else {
    ledBrightness = 0;
  }
  
  analogWrite(ledPin, ledBrightness);
  delay(100);
}