int ledPins[] = {2, 3, 4, 5, 6, 7, 8};  
int brightness = 0;
int fadeAmount = 1;

void setup() {
  for (int i = 0; i < 7; i++) {
    pinMode(ledPins[i], OUTPUT);
  }
}

void loop() {
  for (int i = 0; i < 7; i++) {
    analogWrite(ledPins[i], brightness); 
    delay(30);
  }

  brightness = brightness + fadeAmount;  

  if (brightness <= 0 || brightness >= 255) {
    fadeAmount = -fadeAmount;  
  }
}