int ledPin[] = {13, 12, 11,10};
int ledDelay[4]={8000, 4000,2000, 1000};
// declare other required variables
int currTime ;
int T1 ;
int T2 ;
int T3 ;
int T4 ; 
int LedState0 = HIGH;
int LedState1= HIGH ;
int LedState2= HIGH ;
int LedState3= HIGH ;

void setup() {
  for(int i=0;i<4;i++){
    pinMode(ledPin[i] , OUTPUT);
  }
}


void loop() {
  currTime=millis();
  if (currTime-T1>ledDelay[0]){
     digitalWrite(ledPin[0],LedState0);
    T1=currTime;
    LedState0 = !LedState0 ;
  }
  if (currTime-T2>ledDelay[1]){
     digitalWrite(ledPin[1],LedState1);
    T2=currTime;
    LedState1 = !LedState1 ;
  }
  if (currTime-T3>ledDelay[2]){
     digitalWrite(ledPin[2],LedState2);
    T3=currTime;
    LedState2 = !LedState2 ;
  }
  if (currTime-T4>ledDelay[3]){
     digitalWrite(ledPin[3],LedState3);
    T4=currTime;
    LedState3 = !LedState3 ;
  }
  
  

}