#define LED1_PIN 4
#define LED2_PIN 3
#define LED3_PIN 2
#define LED4_PIN 1
#define TASTER_UP_PIN 5
#define TASTER_DOWN_PIN 6

int LED_value = 0;
unsigned long current_time = 0;
unsigned long previous_time = 0;
bool button_up_state;
bool button_down_state;

void setup() {
  pinMode(LED1_PIN, OUTPUT);
  pinMode(LED2_PIN, OUTPUT);
  pinMode(LED3_PIN, OUTPUT);
  pinMode(LED4_PIN, OUTPUT);
  pinMode(TASTER_UP_PIN, INPUT);
  pinMode(TASTER_DOWN_PIN, INPUT);
  Serial.begin(9600);
}

void update_LEDs(int value) {
  digitalWrite(LED1_PIN, bitRead(value, 0) ? HIGH : LOW);
  digitalWrite(LED2_PIN, bitRead(value, 1) ? HIGH : LOW);
  digitalWrite(LED3_PIN, bitRead(value, 2) ? HIGH : LOW);
  digitalWrite(LED4_PIN, bitRead(value, 3) ? HIGH : LOW);
}

void loop() {
  current_time = millis();
  button_up_state = digitalRead(TASTER_UP_PIN);
  button_down_state = digitalRead(TASTER_DOWN_PIN);

  if (current_time - previous_time >= 100) {
    if (button_up_state == HIGH) {
      LED_value++;
    }
    if (button_down_state == HIGH) {
      LED_value--;
    }
    previous_time = current_time;
  }

  LED_value = max(LED_value, 0);
  LED_value = min(LED_value, 15);

  update_LEDs(LED_value);

  Serial.println(LED_value);
}