int ledPin = 4; // starting LED pin
int ledDelay = 100; // delay between LED state changes
bool reverseLed = false; // flag for changing LED direction

void setup() {
  for (int i = 4; i < 14; i++){
    pinMode(i, OUTPUT);
  }
  pinMode(2, INPUT_PULLUP);
}

void loop() {
  digitalWrite(ledPin, !digitalRead(ledPin));
  delay(ledDelay);

  if (!digitalRead(2)) {
  reverseLed = !reverseLed; // toggle LED direction
  //delay to prevent double click
  delay(200);
}

if ((reverseLed && ledPin == 4) || (!reverseLed && ledPin == 13)){
  ledPin = reverseLed ? 14 : 3; // change direction
}
else {
  ledPin += reverseLed ? -1 : 1; // continue in current direction
}
}