// Code from Optimizing Arduino Code: no setup(), no loop()
// https://youtu.be/-XPrSScamXc

int main() {
  // initialize digital pin LED_BUILTIN as an output.
  DDRB = 0xff;
  while (true) {
    PINB = 0xff;
    for (long i = 0; i < 500000; i++) {
      asm("");
    }
  }
}