//variables
const unsigned int LEDstart = 6;
const unsigned int pause = 400;
const unsigned int LEDcount = 7;
const unsigned int LEDend = LEDcount+LEDstart-1;
const int buttonPIN = 4;
int LEDactive = LEDstart;
int step = 1;
int i;
 
 
void setup() {
  pinMode(4, INPUT); //set pin 4 as INPUT (button)
  Serial.begin(9600); //serial monitor setup
 
  //assign pins
  for(int pin = LEDstart; pin < LEDcount; pin++)
  {
    pinMode(pin, OUTPUT);
    digitalWrite(pin, LOW);
  }
}
 
void loop() {
 
  for( i = 0; i <= 2; i++) //activate LED area(because 0,1,2 are 3 LEDs)
  {
    if(LEDstart <= LEDactive-i*step && LEDactive-i*step <= LEDend) //LEDactive-i*step = LEDactive-0*step(erste LED die an ist) + LEDactive-1*step (zweite LED die an ist) + LEDactive-2*step (dritte LED die an ist)
    {
      digitalWrite(LEDactive-i*step, HIGH);
    
    }
  }
 
  delay(pause);
  int buttonPushed = digitalRead(buttonPIN);
 
  if(buttonPushed == HIGH) //check button press
  {
    for(i = 0; i <= 2; i++) //deactivate LED area
    {
      if(LEDstart <= LEDactive-i*step && LEDactive-i*step <= LEDend)
      {
        digitalWrite(LEDactive-i*step, LOW);
      }
    }
 
    //setup for changing the direction
    LEDactive += step;
    if(LEDactive == LEDstart-3 || LEDactive == LEDend+3)
    {
      step *= -1;
      LEDactive += 2*step;
    }
  }
}