“This is an easy little project for Arduino beginners that only costs about $12 to make. When a person enters the correct code on the keypad, the box will play a secret message. It could be used as part of a scavenger hunt or could be modified to trigger a door to open or trigger a servo with just a few changes. I used an Arduino Mini Pro for my project, but I think an Arduino Nano is a better choice for most beginners because it has a build in USB port for easy programming, so I wrote this instructable with that in mind even though some of my pictures show a Mini Pro.”