const int ledPin = 13;
int brightness = 0;        // Simulated brightness level (0–255)
int fadeAmount = 5;        // How much to change brightness each cycle

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

void loop() {
  // Simulate brightness by adjusting ON time
  digitalWrite(ledPin, HIGH);
  delay(brightness / 10);  // ON duration scales with brightness

  digitalWrite(ledPin, LOW);
  delay((255 - brightness) / 10);  // OFF duration scales inversely

  // Update brightness
  brightness += fadeAmount;
  if (brightness <= 0 || brightness >= 255) {
    fadeAmount = -fadeAmount;  // Reverse direction
  }
}