How to play 3DS games in a dual-screen format on Steam Deck using the Citra Emulator

The Steam Deck, Valve's latest handheld gaming computer, continues to amaze gamers with the amount of power it packs in such a compact form. In addition to full support for many popular Steam games, the modular nature of both the hardware and software has allowed users to tailor their gaming experiences based on their needs and requirements. This also includes third-party software and applications, with one such case emerging in the form of emulators.

Players have been able to set up emulation for various gaming devices, from Sony's PS1 to the Nintendo Wii. Similarly, modern Nintendo console emulation has also cropped up on the Steam Deck, such as the Nintendo 3DS. After all, the popular dual-screen, parallax 3D device from the Mario publisher is essentially a legacy platform now. This guide walks you through setting up the Citra Nintendo 3DS emulator for the Steam Deck, allowing you to use the Deck's display as the bottom screen for more authentic gameplay.

The Nintendo 3DS' dual-screen experience can be enjoyed using a Steam Deck and main monitor

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For the uninitiated, an emulator is an application that mimics the hardware functionality of a device through software. In simpler terms, as far as gaming console emulators are concerned, a PS2 emulator tricks your PC into thinking it is a PS2, which allows it to run games from that console.

WIth that said, here are the requirements that players need before they can get started:

The installed Citra emulator (can be done via Emudeck, a utility simplifying the process of downloading and installing emulators on the Steam Deck and SteamOS, in general)
Legally owned and dumped Nintendo 3DS game ISOs - While emulation is legal, the distribution of their games is not; we do not condone piracy of games, so make sure to purchase the games for emulation
A monitor to connect to for display
Keyboard and mouse for the installation process

1) Setting up the display

Configure the main display (Image via Valve)

First, we will need to set up the discreet monitor as the primary screen. This can be done using the in-built display settings on the Steam Deck. Users must make sure to set up the secondary screen of the Deck to the right. They must also take note of the resolution for each display, with 1080p (1920 x 1080) for the primary monitor and the native 800p (1200 x 800) for the Steam Deck being a stable configuration.

2) Configuring Citra

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Assuming that Citra is installed via Emudeck, the following path is where users can find the configuration files.

Home > .var > app > org.citra_emu.citra > config > citra-emu

Step 1: Make a copy of the qt-config.ini file and rename it to qt-config_old.ini. This is essentially a backup to revert to the default settings, if needed.

Step 2: Open qt-config.ini with KWrite, the default text editor

Step 3: Scroll down to the Layout section (at line 257)

Step 4: Copy and paste the following parameters (for a 1080p screen) under the [Layout] section in your qt-config.ini file.

[Layout]

custom_bottom_bottom=800

custom_bottom_bottom\default=false

custom_bottom_left=1920

custom_bottom_left\default=false

custom_bottom_right=3200

custom_bottom_right\default=false

custom_bottom_top=0

custom_bottom_top\default=false

custom_layout=true

custom_layout\default=false

custom_top_bottom=1080

custom_top_bottom\default=false

custom_top_left=0

custom_top_left\default=true

custom_top_right=1920

custom_top_right\default=false

custom_top_top=0

custom_top_top\default=true

factor_3d=0

factor_3d\default=true

filter_mode=true

filter_mode\default=true

layout_option=1

pp_shader_name=none (builtin)

pp_shader_name\default=true

render_3d=0

render_3d\default=true

swap_screen=false

swap_screen\default=true

upright_screen=false

upright_screen\default=true

3) Setting up the controller

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Since the discreet monitor will be the main screen for emulation, players will also need to set up their key bindings for the Deck. This can be done via the Desktop Mode and then Settings > Controller > Desktop Configuration.

Also, make sure to set your taskbar to "Auto Hide or Windows Can Cover" for bother-free gameplay. Do this by right clicking on the taskbar and selecting "Enter Edit Mode". Then, click on More Options > Auto Hide or Windows Can Cover.

Jumping into the gameplay

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Finally, Citra is now ready to be launched. It can be booted through Steam or the Apps Menu. Users can then select the directory where the game is located and boot it. Before this, ensure that "Single Window Mode" is set to Off under the "View" settings. If the game boots in a small window, just drag it out and fill the main screen. With these settings, the main display should render at 1080p while the bottom Steam Deck screen is at 800p. The latter is reserved for menus and inventory management in most 3DS games and this way, players can use the Steam Deck as the bottom part of the 3DS, including the touchscreen, while enjoying higher resolution gameplay on the main display.