//Initilize Vars
const int  ButtonUp = 12;
const int  ButtonDown = 11;
boolean lastButtonUp = LOW;
boolean lastButtonDown = LOW;
boolean currentButtonUp = LOW;
boolean currentButtonDown = LOW;
int ledState = LOW;
unsigned long previousMillis = 0;
long Hz = 9;
long interval = 1000/(2);

void setup(void) {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(ButtonUp, INPUT_PULLUP);
  pinMode(ButtonDown, INPUT_PULLUP);
  pinMode(2,OUTPUT);

}

void loop() {

  buttonPushed();
  blinkLED(interval/Hz);

}

void buttonPushed(){
  //Check if Up Button is pushed
  currentButtonUp = digitalRead(ButtonUp);
  if(lastButtonUp == LOW && currentButtonUp == HIGH && Hz < 999)
  {
    Hz = Hz + 1;
    //Serial.println(Hz);
  }

  lastButtonUp = currentButtonUp;

  //Check if Down Button is pushed
  currentButtonDown = digitalRead(ButtonDown);
  if(lastButtonDown == LOW && currentButtonDown == HIGH && Hz > 0)
  {
    Hz = Hz - 1;
    //Serial.println(Hz);
    if (Hz == 0){
      ledState= HIGH;
    }
  }
  lastButtonDown = currentButtonDown;

}

void blinkLED(const long interval) {
//Serial.println(interval);
 unsigned long currentMillis = millis();

  if (currentMillis - previousMillis >= interval){
    previousMillis = currentMillis;

    if (ledState == LOW){
      ledState = HIGH;
    }
      else {
        ledState = LOW;
    }

    }
    digitalWrite(2, ledState);

}