Awesome!  Also, thanks for the link, I'm always looking for accessible hacking games.  I had been using picoctf.org and tryhackme.com mainly, before this.


SimpleStacker

You could use a Raspberry Pi to control a servo that then unlocks something like in this video:

You can program the RPi with a Linux console to only unlock when a challenge was solved.

For challenges, depending on the age of your kid, you could try to setup a few from 

https://overthewire.org/

security

[Parents Corner] How would you set up a hackable safe?

Cool idea!

You could use a Raspberry Pi to control a servo that then unlocks something like in this video:

https://www.youtube.com/watch?v=utDbTba_b5o

You can program the RPi with a Linux console to only unlock when a challenge was solved.

For challenges, depending on the age of your kid, you could try to setup a few from https://overthewire.org/ on the RPi. 