Arduboy is a miniature game system the size of a credit card. It comes installed with a classic 8-bit game and can be reprogrammed from a library of open source games available online. Arduboy is open source so you can learn to code and create your own games.
It's very easy to use. Install the drivers, connect it via USB and put your games on.
It's also easy to learn to code for.
To get a quick overview, check this website:
You can also download games there.
We recommend to use the Arduboy Manager:
BTW: There's an RPG being developped for it!