Touhou 6: Embodiment of Scarlet Devil — Nintendo Switch Port

(東方紅魔郷　〜 the Embodiment of Scarlet Devil)

A native homebrew port of ZUN's legendary 2002 bullet hell danmaku masterpiece Touhou 6: Embodiment of Scarlet Devil for the Nintendo Switch (Horizon OS).

Built upon the cross-platform decompilation engine GensokyoClub/th06, this port features custom hardware-accelerated OpenGL ES 3.2 rendering over Nouveau/Mesa, seamless Nintendo Switch Joy-Con and Pro Controller support, native 1280x720 window resolution scaling with pure OLED black letterbox borders, and an intelligent filename alias resolver designed for FAT32 SD cards.

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✨ Key Features

• 🚀 Full 60 FPS Performance: Smooth, rock-solid 60 FPS danmaku gameplay across all Nintendo Switch models (V1 Erista, V2 Mariko, Switch Lite, Switch OLED) running natively on Horizon OS—no Linux, Box64, or Wine required.
• 🦇 Embedded Official Artwork: Features the classic 2002 CD release cover silhouette embedded directly within the .nro asset header for seamless display in Homebrew Menu, Sphaira, and custom home screen forwarders.
• 🖥 OLED-Optimized Widescreen Scaling: Automatically scales the original 640x480 gameplay viewport centered inside the Switch's native 1280x720 display. Double-buffered hardware scissor testing (GL_SCISSOR_TEST) guarantees that the 16:9 side pillarboxes remain 100% pure black (#000000), preserving contrast and extending battery life on OLED screens.
• 🎮 Native Controller Support: Seamless out-of-the-box mapping for Joy-Con (Handheld, Grip, or detached) and Nintendo Switch Pro Controllers via SDL2 GameController API, complete with slow-motion focus mode (L/R/ZL/ZR) and menu navigation.
• 🧠 Defensive Smart Filename Resolver: FAT32/ExFAT filesystems on Switch often reject Japanese Shift-JIS / UTF-8 characters (東方紅魔郷.cfg), and Windows extraction tools frequently strip non-ASCII prefixes from filenames (紅魔郷CM.DAT → CM.DAT). The engine includes a low-level filesystem interceptor that automatically locates and resolves stripped ASCII filenames (CM.DAT, MD.DAT, .cfg, th06.cfg) transparently.
• 🎵 Lossless Audio & BGM Support: Full support for sound effects (CM.DAT) and lossless WAV background music playback (bgm/ folder).

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📥 Installation Guide

⚠️ Disclaimer: In compliance with ZUN's guidelines and copyright law, this repository contains ONLY the homebrew engine code. Game asset archives (*.DAT) are not distributed. You must legally own a copy of Touhou 6: Embodiment of Scarlet Devil v1.02h.

1. SD Card File Structure

1. Ensure your Nintendo Switch is running custom firmware (Atmosphère CFW).
2. Download the latest touhou6.nro from the Releases tab (or build from source).
3. Create a folder named sd:/touhou6/ on your SD card and copy touhou6.nro into it.
4. Copy the data archives from your legitimate Touhou 6 PC folder directly into the same directory:

   sd:/touhou6/
       ├── touhou6.nro       # Nintendo Switch homebrew executable
       ├── CM.DAT            # Game data (or 紅魔郷CM.DAT)
       ├── ED.DAT            # Endings data (or 紅魔郷ED.DAT)
       ├── IN.DAT            # Stage intro data (or 紅魔郷IN.DAT)
       ├── MD.DAT            # MIDI/Music data (or 紅魔郷MD.DAT)
       ├── ST.DAT            # Stage data (or 紅魔郷ST.DAT)
       ├── TL.DAT            # Title screen data (or 紅魔郷TL.DAT)
       └── msgothic.ttc      # Japanese font (optional)
   

   (Note: Whether your files are named with full Japanese characters 紅魔郷CM.DAT or stripped ASCII CM.DAT, the engine will locate and load them automatically).

2. Enabling Background Music (BGM)

Because Horizon OS lacks a system MIDI synthesizer, Touhou 6 plays background music on the Switch via ZUN's official WAV music mode:

1. Locate or download the standard Touhou 6 EoSD WAV BGM / Lossless Soundtrack Pack.
2. Create a folder named bgm inside your game directory (sd:/touhou6/bgm/).
3. Place all soundtrack WAV files (th06_01.wav through th06_17.wav) along with their loop point definition files (*.pos) inside bgm/.
4. Launch the game. The engine will automatically detect bgm/th06_01.wav, configure musicMode to WAV, and play full soundtrack audio. (If needed, navigate to Options -> BGM inside the game menu and set it to WAV).

3. Launching

Run touhou6.nro from the Homebrew Menu (hbmenu), Sphaira launcher, or install a home screen forwarder shortcut.

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🕹 Controls

Nintendo Switch Button	Action
Left Stick / D-Pad	Character Movement
A (or B)	Shoot / Confirm
B (or A)	Bomb / Cancel
L / R / ZL / ZR	Focus (Precision Slow-Motion Movement)
+ (Plus)	Pause / In-Game Menu

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🛠 Building from Source

Automated Build (GitHub Actions)

This repository includes a pre-configured GitHub Actions CI pipeline (.github/workflows/build-switch.yml). Simply fork or push this repository to GitHub, and the CI workflow will automatically compile touhou6.nro inside an official devkitA64 container and upload the ready-to-play executable as a downloadable workflow artifact.

Local Build (Linux / macOS / WSL)

1. Install devkitPro with devkitA64 and libnx.
2. Install required Switch portlibs:

   sudo dkp-pacman -Syu
   sudo dkp-pacman -S switch-sdl2 switch-sdl2_image switch-sdl2_ttf switch-mesa switch-libdrm_nouveau switch-libpng switch-libjpeg-turbo switch-freetype switch-zlib

3. Set environment variables and compile:

   export DEVKITPRO=/opt/devkitpro
   export PATH=$DEVKITPRO/tools/bin:$PATH
   
   # Pre-generate shader header embeds
   python3 scripts/gen_embeds.py
   
   # Build executable
   make -j$(nproc)

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🤝 Credits & Acknowledgments

• ZUN / Team Shanghai Alice — Original creator and developer of the Touhou Project series.
• GensokyoClub — For their monumental work on the byte-accurate C++ portable decompilation of Touhou 6.
• Switchbrew & devkitPro Team — For the open-source libnx SDK and Nintendo Switch toolchain.