int ledPins[] = {10, 9};
int ledAmount = 2;

int btnPin = 2;
int btnState = 0;
boolean isBtnPressed = false;
int counter = 0;
void setup() {
  // put your setup code here, to run once:
  for(int i=0; i<ledAmount; i++){
    pinMode(ledPins[i], OUTPUT);
    digitalWrite(ledPins[i], LOW);
  }
  pinMode(btnPin, INPUT);
  Serial.begin(9600);
}

void loop() {
  // check the button
  btnState = digitalRead(btnPin);

  // check if the state is different from the previous loop

  if (btnState == HIGH && isBtnPressed == false) {
    // add one to the counter
    counter++;
    isBtnPressed = true;
    // check if the counter is too large
    if(counter>ledAmount){
       counter = 0;
    }
    Serial.println(counter);
  }else if(btnState == LOW){
    isBtnPressed = false;
  }

  for(int i=0; i<ledAmount; i++){
    if(counter >= i+1){
      digitalWrite(ledPins[i], HIGH);
    }else{
      digitalWrite(ledPins[i], LOW);
    }
  }

  // delay helps to prevent noise from the input signal
  // even better way to do this would be to implement debouncing:
  // https://www.arduino.cc/en/Tutorial/BuiltInExamples/Debounce
  delay(10);
}