#define LED_PIN 9        // PWM pin
#define POT_PIN A0       // Potentiometer

void setup() {
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  int potValue = analogRead(POT_PIN);      // 0–1023
  int brightness = map(potValue, 0, 1023, 0, 255);
  analogWrite(LED_PIN, brightness);        // PWM output
}