int ledPin[] = {13, 12, 11,10};
int ledDelay[4]={8000, 4000,2000, 1000};
// declare other required variables
unsigned long lastToggle[4] = {0, 0, 0, 0};
const unsigned long intervals[4] = {1000, 2000, 4000, 8000};

void setup() {
  for(int i=0;i<4;i++){
    // initialize lastChangeTimes
    pinMode(ledPin[i], OUTPUT);
    // set pin mode for ledPins
    
  }
}


void loop() {
  unsigned long currentMillis = millis();
  for (int i = 0; i < 4; i++) {
    if (currentMillis - lastToggle[i] >= intervals[i]) {
      digitalWrite(ledPin[i], !digitalRead(ledPin[i]));
      lastToggle[i] = currentMillis;
    }
  }
}