Our Computer Science 2 Class needs a screen lock for our Retropie, we only know the basics of Java and Python. We need a code to add to our Retropie that will lock the screen but not crash after 2 and 1/2 minutes. (If more money is inputted the screen unlocks.)

This are the assignment instructions:

You need to find a program or write code that will lock the screen on our RetroPie after 2 and 1/2 minutes (whether or not it is in use, not just idle). If it can be password protected that would be best (or if we can add it later). You can use Python, Java, or whatever you can find. You might use some code out there and adjust, or start your own.

OS: RetroPie 3.5
Emulator I want it to work for the most (I want it to be for all, but if it had to be just one): AdvanceMAME
Hardware: Using Raspberry 1 B