3 LED berjalan arduino uno r3

3 LED berjalan

const int ledPin13 =  13;      // the number of the LED pin
const int ledPin12 =  12;      // the number of the LED pin
const int ledPin11 =  11; 

unsigned long prev1 = 0;
unsigned long prev2 = 0;
unsigned long prev3 = 0;

int ledState11 = HIGH;
int ledState12 = LOW;
int ledState13 = LOW;

void setup() {
  // put your setup code here, to run once:
    pinMode(ledPin12, OUTPUT);
    pinMode(ledPin13, OUTPUT);
    pinMode(ledPin11, OUTPUT);
    digitalWrite(ledPin11, ledState11);
    digitalWrite(ledPin12, ledState12);
    digitalWrite(ledPin13, ledState13);
}

void loop() {
  unsigned long curr = millis();
 
  if (curr - prev1 >= 2000) {
    if (ledState11 == HIGH && ledState12 == LOW && ledState13 == LOW) {
        ledState11 = LOW;
        ledState12 = HIGH;
        ledState13 = LOW;
    }
    else
    if (ledState11 == LOW && ledState12 == HIGH && ledState13 == LOW) {
        ledState11 = LOW;
        ledState12 = LOW;
        ledState13 = HIGH;
    }
    else
    if (ledState11 == LOW && ledState12 == LOW && ledState13 == HIGH) {
        ledState11 = HIGH;
        ledState12 = LOW;
        ledState13 = LOW;
    }
    digitalWrite(ledPin11, ledState11);   
    digitalWrite(ledPin12, ledState12);   
    digitalWrite(ledPin13, ledState13);   
   
    prev1 = curr;
  }
}