#define LDR_PIN A0
#define LED_PIN D9  

int ldrValue;
int ledBrightness;

void setup() {
  Serial.begin(115200);
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  ldrValue = analogRead(LDR_PIN);
  ledBrightness = map(ldrValue, 200, 900, 0, 255);
  ledBrightness = constrain(ledBrightness, 0, 255);
  analogWrite(LED_PIN, ledBrightness);
  delay(100);
}