2DS/3DS mod using a micro controller

Hey everyone, I've been working on modding a Nintendo 2DS to work with a Gamecube controller. I recently came across these videos:

I've been in contact with the guy who did this mod because it's very close to the idea I had on doing this. He recommended buying a Teensy 3.1 or a Arduino microcontroller to do the job.

Now I'm wondering does anybody have any tips on how to do what he's done? Using the Teensy 3.1 or Arduino of course. Second question does anybody know where I could get a program code to use on a microcontroller to use for this. I've seen a few different tutorials on programming the Teensy for controller use.
(Example Overview | USB SNES Gamepad | Adafruit Learning System)
Lastly I don't know much about Arduino could anybody recommend a good microcontroller for this project?
I appreciate any help I can get. Thank you!

I'm not a gamer. What does 2DS & 3DS mean exactly , in terms of functionality ?
(what exactly IS this MOD you refer to ?)
Can you just explain what the mod entails in electronics terms ?

Hi thanks for the reply. I am sorry for the confusion, when I say 2DS and 3DS I'm referring to the Nintendo handheld system the Nintendo 3DS. I'm not too great with electrical terms. Basically I'm trying to do what the guy did in the video. I want to hook up all the buttons on the nintendo 3DS to the microcontroller the from the micro controller connect a receiver for a video game controller. If that makes sense.

Something like this

Here are some examples of what I'm trying to do.


Except I want the gamecube controller to be the input device for the Nintendo 3DS system.