millis() > delay() on Arduino

delay-blink.c

#include <Arduino.h>

#define PIN_LED 13
#define LED_STATE_SWITCH_INTERVAL 500  // milliseconds between LED state change

void setup(void) {
    pinMode(PIN_LED, OUTPUT);
    digitalWrite(PIN_LED, LOW);
}

void loop(void) {
    digitalWrite(PIN_LED, HIGH);
    delay(LED_STATE_SWITCH_INTERVAL);
    digitalWrite(PIN_LED, LOW);
    delay(LED_STATE_SWITCH_INTERVAL);
}