The biggest obstacle I encountered was getting the piezo buzzer to work. Initially, I wanted the piezo buzzer to play a tune for the alarm, but I didn't realize that the tone() function could only be used with specific pins. I played around with the wiring and code for a while before I found, through the Spark webpage, that tone() only works with specific output pins. I also found that you can simply turn the buzzer on and off by sending a digital high and low signal. I chose to use this simpler method because it made the buzzer louder and more annoying, which should better alert the homeowners and drive away the invaders or intruders.