#define red 13
#define amber 12
#define green 11

void setup() {
  Serial.begin(9600);

  pinMode(red, OUTPUT);
  pinMode(amber, OUTPUT);
  pinMode(green, OUTPUT);

  digitalWrite(red, HIGH); // Start with red light
}

void loop() {
  if (Serial.available() > 0) {
    char received = Serial.read();
    if (received == 'a') {
      Serial.println("Caution");

      // Assembly language block for more efficient light control
      asm volatile(
        "ldi %[delay_value], 200 ; Set delay value to 200\n"
        "sbi %[port_amber], %[pin_amber] ; Turn on amber light\n"
        "call delay_func ; Call delay function\n"
        "cbi %[port_red], %[pin_red] ; Turn off red light\n"
        "cbi %[port_amber], %[pin_amber] ; Turn off amber light\n"
        "sbi %[port_green], %[pin_green] ; Turn on green light\n"
        "call delay_func ; Call delay function\n"
        "sbi %[port_amber], %[pin_amber] ; Turn on amber light\n"
        "cbi %[port_green], %[pin_green] ; Turn off green light\n"
        "call delay_func ; Call delay function\n"
        "cbi %[port_amber], %[pin_amber] ; Turn off amber light\n"
        "sbi %[port_red], %[pin_red] ; Turn on red light\n"
        "call delay_func ; Call delay function\n"
        "rjmp end_assembly ; Jump to the end of the assembly block\n"
        "delay_func: ; Delay function label\n"
        "dec %[delay_value] ; Decrement delay_value\n"
        "brne delay_func ; Repeat delay_func if delay_value is not zero\n"
        "ret ; Return from delay_func\n"
        "end_assembly: ; End of assembly block\n"
        :
        : [port_red] "I" (_SFR_IO_ADDR(PORTB)), [pin_red] "I" (PORTB5),
          [port_amber] "I" (_SFR_IO_ADDR(PORTB)), [pin_amber] "I" (PORTB4),
          [port_green] "I" (_SFR_IO_ADDR(PORTB)), [pin_green] "I" (PORTB3),
          [delay_value] "r" (0)  // Corrected specification for %[delay_value]
      );

      Serial.println("RED light is on");
      Serial.println("---------------------------------");
    }
  }
}