Arduino onboard LED minute/second timer

minute_second_timer.ino

unsigned long lastTime = 0;
int seconds = 0;
int minutes = 0;

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

void loop() {
if (millis() - lastTime >= 1000) {
lastTime = millis();
seconds++;

if (seconds >= 60) {
seconds = 0;
minutes++;

// Long flash to signal a new minute
digitalWrite(LED_BUILTIN, HIGH);
delay(500);
digitalWrite(LED_BUILTIN, LOW);

} else {
// Short blink every second
digitalWrite(LED_BUILTIN, HIGH);
delay(50);
digitalWrite(LED_BUILTIN, LOW);
}

Serial.print(minutes);
Serial.print("m ");
Serial.print(seconds);
Serial.println("s");
}
}