const int POT=A0, LED_RED=8, LED_GRN=9;

void setup() {
  pinMode(LED_RED,OUTPUT);
  pinMode(LED_GRN,OUTPUT);
  Serial.begin(9600);
}

void loop() {
  int raw = analogRead(POT);
  Serial.print("ADC="); Serial.println(raw);

  if (raw < 300) {
    digitalWrite(LED_RED, HIGH); // "Tối"
    digitalWrite(LED_GRN, LOW);
  } else if (raw > 700) {
    digitalWrite(LED_RED, LOW);  // "Sáng"
    digitalWrite(LED_GRN, HIGH);
  } else {
    digitalWrite(LED_RED, LOW);  // Bình thường
    digitalWrite(LED_GRN, LOW);
  }
  delay(100);
}