LED Police chaser code

Using Arduino Programming Questions
4

consider

#define MyHW
#ifdef MyHW
const int LED_Red  = 13;
const int LED_Blue = 12;

const int pinBut   = A1;

#else
const int LED_Red = 7;
const int LED_Blue = 11;
#endif

#define Period   250
unsigned long msecLst;

byte          butState;
bool          enable = true;

// -----------------------------------------------------------------------------
void setup () {
    pinMode (pinBut,   INPUT_PULLUP);

    pinMode (LED_Red,  OUTPUT);
    pinMode (LED_Blue, OUTPUT);

    digitalWrite (LED_Red,  HIGH);
    digitalWrite (LED_Blue, LOW);
}

// -----------------------------------------------------------------------------
void
loop ()
{
    unsigned long msec = millis ();

    if (enable && (msec - msecLst) > Period)  {
        msecLst = msec;

        digitalWrite (LED_Red,  ! digitalRead (LED_Red));
        digitalWrite (LED_Blue, ! digitalRead (LED_Blue));
    }

    byte but = digitalRead (pinBut);
    if (butState != but)  {
        butState = but;
        delay (10);         // debounce

        if (LOW == but)
            enable = ! enable;
    }
}