All the links and sources are at the end of this comment.
It goes without saying, you need a modded Switch in order to achieve this. More specifically, one that was prepared to (also) run Android. In my particular case, I use Android 10, but guess it will work the same way if you update to 11.
The original concept comes from a tutorial by AeliusDawn about running Citra on your PC using your main monitor as the top screen and a smartphone as a touch screen. While this is nice in its own way, there are two drawbacks here.
First, the screen size, depending on your device, may be kinda small (though I guess you could use a tablet too?) unless you have a flagship or a rather newish phone. Yes, I know the touch screen on the 3DS is kinda small too. But why stay small when we can go big?
And second, a smartphone/tablet lacks buttons, forcing you to still use your keyboard or a joystick, making the experience actually worse cause now you need more peripherals to play the same games, making this more a proof of concept than something actually viable to be used in normal basis.
So, following the tutorial by AeliusDawn, I got everything ready on my PC and my Switch. In order to be able to use the joycons, I had to individually synchro both of them with my PC and map the buttons inside Citra.
The problem here is, once the joycons are attached into the console, they automatically turn off any kind of bluetooth signal and forcedly synchro back with the console (doesn't matter if you're on Android or Horizon on sysnand or emunand), so you have to detach them in order to use them. Or, if you're like me and wanna use them as a console, simply lift the joycons a little but leave them in the rails. As long as the contacts on the bottom aren't touching with the ones of the console, the joycons won't automatically synchro back. You can see I'm struggling a little to keep my right joycon in place cause the rail is wasted (I can take the joycon off withot pressing the back button to release it), but the left one stays in place just fine, so you won't have any problems if your console is in a better shape than mine (also, to be fair, I was in a really uncomfortable position, with my phone recording just in front of my face and my arms around the tripod, but I don't have that many problems when I'm sitting like a normal human being).
Once everything is set, you can enjoy a fairly decent and interesting way to revisit your 3DS favourites. Think of this as, in someway, what a potential 3DS VC could've been on the WiiU.
Clarifications
- When setting Borderless Gaming, the "Applications" list was showing several Citra Nightly instances (3~5), and none named as the HEAD or anything related. Keep in mind, AeliusDawn's tut is from late 2021, so of course there were gonna be differences. To avoid struggling finding the right instance in the list, I simply added all of them and applied the same configuration.
- The image on my Switch screen is stretched. The bottom screen on a 3DS/XL/New/New XL is always 4:3, while the Switch's is 16:9. You can fix that by simple changing into a custom resolution of 690x720 if you wanna use the whole height of the screen while keeping the aspect ratio (the rest of the space would simply be black, afaik, not Desktop).
- You can see there's a little lag between my touch screen inputs and the response. According to what I read, you can lower the latency by reducing the resolution of the custom screen, by I wouldn't expect some instant response anyway. Better not use this method is you're gonna play games that require high precision and quick-response timing.
- I bumped Citra's internal resolution to make the games look better. In this particular case, I'm also using part (not all of it) of an HD textures pack for Pokémon ORAS while also enabling the cheat code to remove the black outlines for the 3D models.
- Yes, my Kirlia is called Waifu. No, I have no regrets.
- Yes, I launch my roms from Steam. Because I can. I'll leave a link down here, so you can do that as well. The video tut is intended for Citra on the Steam Deck, but there are plenties of other emulators you can set up as well, and it works just the same on Windows.
Links of interest
- Switchroot's Official Guide for Android 10 Installation on Switch.
- [YouTube] Citra Tutorial / Use Your Phone As The Bottom 3DS Screen, by AeliusDawn.
- SpaceDesk Download Page for All Platforms.
- Official Borderless Gaming Repository on GitHub.
- Pokémon Omega Ruby/Alpha Sapphire HD Texture Pack and No Black Outline Cheat Codes (Search on the OP under the P).
- Steam ROM Manager and How to set it up.
