   const uint8_t LCD_COLUMNS = 20, LCD_ROWS = 4;
 
   wpb.begin();
-  wpb.turnLEDOn();
+  wpb.turnLEDOn();                //
 
   pinMode(MOTOR_PIN, OUTPUT);
   pinMode(POT_PIN, INPUT);


void loop()
{
                                                      //*** static local variables--i.e. static variables inside of functions--are NOT STACK VARIABLES;
                                                      //    their values persist even after function ends, as long as the program is still running
                                                      //*** also, static local variables still only have local scope
                                                      //*** perform operations with data of the same type, so as to boost performance by not needing to typecast
  static unsigned long setDuration;                   // the duration that the centrifuge should run
  static unsigned long spinningStartTime;             // point on the timeline where the countdown starts, i.e. when wpb is pressed the second time
  static uint8_t motorSpeed;

        lcd.setCursor(0, 1);
        lcd.print(F("Finished in: "));
        changedUIString = true;
        Serial.println("reached only once");
      }

      unsigned long secondsLeft = (setDuration - (millis() - spinningStartTime))/1000;  //*** save RAM AND flash memory by only doing this calculation once per case in loop()
