// int currentTime; // int -> 2 bytes = 16 bits -> 2^15 = 32765
// unsigned int currentTime; // I can store maximum 65676

// long = 2 int = 4 bytes = 32 bits = 2^32
// unsigned long - 50 days
unsigned long currentTime, lastTime;

bool ledState = HIGH;

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  currentTime = millis();

  if (currentTime - lastTime > 5000) {
    lastTime = currentTime;
  }

  if (currentTime - lastTime < 2000) {
    ledState = HIGH;
  }
  else {
    ledState = LOW;
  }

  digitalWrite(LED_BUILTIN, ledState);
}


void blink() {
  currentTime = millis();
  
  Serial.print("currentTime: ");
  Serial.print(currentTime);
  Serial.print("\tlastTime: ");
  Serial.println(lastTime);

  if (currentTime - lastTime > 1000) {
    ledState = !ledState;
    lastTime = currentTime;
  }

  digitalWrite(LED_BUILTIN, ledState);
}

void usingDelay() {
  digitalWrite(LED_BUILTIN, HIGH);
  Serial.println("ON");
  Serial.println(millis());
  delay(1000);

  digitalWrite(LED_BUILTIN, LOW);
  Serial.println("OFF");
  Serial.println(millis());
  delay(1000);
}