void setup() {}

void loop() {
  *(volatile uint8_t*)0x25 = (*(volatile uint8_t*)0x25 & ~0x38) | ((millis() / 0x3E8 & 1) << 5) | ((millis() / 0x1F4 & 1) << 4) | ((millis() / 0xFA & 1) << 3);
}