const int LED1 = 2;
const int LED2 = 4;
const int LED3 = 7;
const int LED4 = 8;
const int LED5 = 12;
const int LED6 = 13;

const int LEDarray[] = {2,4,7,8,12,13};

const int constantInterval = 50;

int curLED = 0;             // ledState used to set the LED

void setup() {
  Serial.begin(9600);
  pinMode(LED1, OUTPUT);
  pinMode(LED2, OUTPUT);
  pinMode(LED3, OUTPUT);
  pinMode(LED4, OUTPUT);
  pinMode(LED5, OUTPUT);
  pinMode(LED6, OUTPUT);
}

void loop() {
  unsigned long currentMillis = millis();
  int input = analogRead(A0);

  int interval = constantInterval;

  //to balance between left and right side
  if(input < 512){
    interval = constantInterval + input;
  }else{
    interval = 512-(input-512) + constantInterval;
  }

  //for debugging purpose (do they affect clock rate?)
//  Serial.println(interval);
//  Serial.println(curLED);

  if (currentMillis - previousMillis >= interval) {
    // save the last time you blinked the LED
    previousMillis = currentMillis;

    //reset the state
    digitalWrite(LED1, LOW);
    digitalWrite(LED2, LOW);
    digitalWrite(LED3, LOW);
    digitalWrite(LED4, LOW);
    digitalWrite(LED5, LOW);
    digitalWrite(LED6, LOW);

    if (input < 512){ //<-- left side
       curLED-=1;
       if (curLED < 0){
          curLED = 5;
    }
    }else{ //<-- right side
      curLED+=1;
      if (curLED > 5){
        curLED = 0;
      }
    }


    //set the curLED on V1
    digitalWrite(LEDarray[curLED], HIGH);
  }
}