//define all the arrays and variables for the code
int leds[] = {10, 9, 8, 7, 6, 5, 4, 3, 2};
const byte ledGreen = 20;
const byte button = 15;
const long delayTimeL = 100;
const long delayTimeB = 1;
unsigned long pastTime = 0;
int act = 0;
int direct = 1;
int numOfLeds = sizeof(leds) / sizeof(leds[0]); 
int go = 1;

void setup() {

//making all the led's pins OUTPUT
  for (int i = 0; i < numOfLeds; i++) {
    pinMode(leds[i], OUTPUT);
  }
}

void reset() {

//making all the leds LOW
  for (int i = 0; i < numOfLeds; i++) {
    digitalWrite(leds[i], LOW);
  }
}

void ledWave() {

  //making the delay between two leds HIGH state and checking if the button is pressed
  unsigned long currentTime = millis();
  if (go == 1) {

  //making HIGH all the leds one by one towards and backwards but the others are in LOW state
      if (currentTime - pastTime >= delayTimeL) {
        reset();
        digitalWrite(leds[act], HIGH);
        act += direct;
        pastTime = currentTime;

        if (act == numOfLeds - 1 || act == 0) {
          direct = -direct;
        }
      }
  }
  else {

//delay is for better visual effect
    reset();
  }
}

void loop() {

  if (digitalRead(button) == HIGH) {
    go++;
  }
  ledWave();
  if (go == 2) {
    for (int k = 1; k < 4; k++) {
      for (int j : leds) {
        digitalWrite(j, HIGH);
      }
      delay(300);
      for (int j : leds) {
        digitalWrite(j, LOW);
      }
      delay(300);
    }
    go++;
  }
  if (go == 3) {
    digitalWrite(ledGreen, HIGH);
  }
}