2 Player Shadow The Hedgehog

A multiplayer mod for Shadow the Hedgehog NTSC-U (GameCube)

About

This project allows you to experience Shadow The Hedgehog (GameCube)'s 1P modes with a second player. Story Mode, Select Mode, Expert Mode, and Last Story are all fully functional

Important

• You must set Dolphin to use 64MB of RAM to play this mod. This is done automatically if you add the GUPE8P.ini file
• If you are playing on a real Wii/GameCube, you must apply the console variant of the mod, which reduces texture sizes to have mostly stable gameplay with only 24MB of RAM
• You can change characters. Select 2P-VS, select characters, then back out to the main menu at the 1-3 round select screen. Your character choices will carry over to 2P CO-OP
• Shadow the Hedgehog: Reloaded - If you are looking to play a 2P version of Reloaded, go here: 2P-Reloaded

How to play / Setup

ROM Validation

This mod is only compatible with the NTSC-U GameCube version

Verify the ROM you are attempting to patch is a 1:1 ShadowTheHedgehog NTSC-U GameCube ISO

GCZ/WIA/RVZ or any other format than ISO is not supported. Please convert to ISO, then compare your game to the table below

You can convert your RVZ game by right-clicking your game in Dolphin's game list -> Convert File...

You can check your hashes by right-clicking your game in Dolphin's game list -> Properties -> Verify tab

ROM	CRC32 Hash	SHA-1 Hash
NTSC-U	f582cf1e	5dc81ad9c97549394e30bedc252bfa37d4db1de0

Summary

1. Patch your original NTSC-U ISO with the .xdelta of your choice
2. Dolphin: Ensure you placed GUPE8P.ini, Enabled Cheats, and set Force Aspect ratio
3. Nintendont: Ensure you placed GUPE8P.gct file next to game.iso, In Nintendont configuration, set Cheats ON and Unlock Read Speed ON
4. Play! See below for detailed steps

Patching

Note: You need the GUPE8P.ini file for the mod to work properly, running just the ISO will not work! If you follow Step 4. of the Dolphin setup, this is part of the GameSettings folder merge step.

1. Download the latest release from here and extract it somewhere you can access easily
2. Visit https://shadowthehedgehoghacking.github.io/xdelta-wasm/ or any other xdelta3 patcher of your choice
3. Select your original ISO as the Source file
4. Select the 2P-ShdTH-[version]-[aspect]-[variant].xdelta file from Patches as the Patch file. Use console variants if playing on real hardware. Use 64M variants if playing on Dolphin
5. Click Apply Patch: It will then 'download' the patched file as ISO NAME-patched.iso (nothing is actually uploaded/downloaded, it is all done on-device)
6. If you run into errors, likely the ISO is wrong hash for the xdelta you downloaded. Double check your original game in Dolphin Verify tab
7. If you want to make additional modifications (such as CharacterMods) follow Extra Mods

Expected Patch Results (v2.5)

PATCH	CRC32 Hash	SHA-1 Hash
64M-WIDESCREEN	0b7edd91	a5d3f1e5631604c929277b734227b92749106bc4
CONSOLE-WIDESCREEN	9df37a91	79b3f45b4cbf4d698ceb62cbe81ba1454795e7c8
64M	6d88d153	8f462508dfefeba57849feea86a726d89facaba7
CONSOLE	388f9f84	fb5547e7c1e490ef0588cdd584b6eee4f8ef5353

Dolphin

1. Get the latest Dolphin Emulator - Dolphin 2506 or newer
2. (Optional) We recommend keeping a separate Dolphin instance just for this mod. Before launching Dolphin, create an empty file portable.txt in the same folder as Dolphin.exe
3. Launch Dolphin. On Dolphin's menu bar, click File -> Open User Folder. The folder that appears is your <Dolphin User Folder> in the below steps
4. Copy/Move the two folders (GameSettings and Load) in Dolphin Configuration (Required) to <Dolphin User Folder>
5. Move/Save the patched ISO you created earlier to the Path Dolphin detects your games. A new 2P Mod Shadow entry should appear in your Dolphin game list, with greater than 0 filesize, and with a custom banner. Use this when playing the game
6. If the game does not appear as you expect, select View -> Purge Game List Cache from Dolphin's menu bar
7. Enable Cheats in Dolphin -> Config. Right click the game the list and choose Properties -> Gecko Codes to change any configuration codes
8. Under Dolphin -> Config -> Advanced enable CPU Clock Override and try various values (CPU dependent). I highly recommend at least 150% if your CPU can handle it. See Dolphin FPS optimization (CPU variable)
9. Set Aspect Ratio in Dolphin -> Graphics -> Aspect Ratio to Force 16:9 or Stretch to Window if playing in Widescreen. Set it to Force 4:3 if playing in Original Aspect Ratio
10. (Optional) To enable Custom Textures: Dolphin -> Graphics -> Advanced Enable Load Custom Textures and Prefetch Custom Textures
11. (Optional) If you want to use the 100% Save, place 8P-GUPE-SHADOWTHEHEDGEHOG.gci GCI file at <Dolphin User Folder>\GC\USA\Card A\ - This is already done if you copy the Dolphin Configuration (Optional) folder, like in step 4

Nintendont (Wii/Wii U)

1. If you want to customize cheats for Nintendont, use CodeManager2 with GUPE8P.ini to generate your own .gct for Nintendont. A GCT is required as the split screen codes are exclusive to these
2. Rename your patched ISO to game.iso and place it on your Nintendont SD/USB
3. For convenience, the release includes pre-built GCTs for Widescreen and Original Aspect in both Vertical and Horizontal split screen modes. If creating your own GCT file and playing with Original Aspect Ratio, you should disable the (Widescreen) code

Copy GUPE8P.gct to the same directory as your game.iso
 e.g. USB:/games/Shadow The Hedgehog [GUPE8P] should have:
   game.iso
   GUPE8P.gct
 in the folder.
Copy 'saves' folder to root of USB or SD (same one where game is)
Nintendont should be configured as follows for the best experience:
   Cheats ON
   Unlock Read Speed ON
 Optional:
   Memcard Emulation ON (If you want to use provided 100% save)
   Video Width (Set to whatever fills your screen without black bars, in my case it was 714)

Dolphin FPS Optimization

Config -> Advanced -> CPU Clock Override slider

Adjust clockspeed while running the game
Note: Dolphin only saves this change for next run if your game is NOT running
You should find the value that runs best, close the game, then set it again

I recommend loading in Glyphic Canyon, have one player stay at the start,
have the other go to the first area with enemies and Knuckles
Try adjusting the slider here to reach 60fps. It will be ~30fps with default 100% clock

It varies per system, some run better with underclock/overclock

I recommend trying 80%, 150%, 200%, 220%, 250%, 270%, 290%, 300% 
Note: Higher clockspeeds may result in audio distortions if your system can't keep up
If audio distortions occur, lower the clockspeed
I use 290% for AMD Ryzen 9 5900X. Previously 217% for AMD Ryzen 7 3800X, 165% for Intel i5-3570k

Extra Mods

After you've patched your ISO with the chosen xdelta, you can make additional modifications. Follow the steps below to use mods such as Sonic over Yellow Android

Extraction of Game / Extracted Game Format

1. Open Dolphin
2. Right-click your 2P-ShdTH ISO you created in the game list
3. Select Properties
4. Select FileSystem Tab
5. Right-click "Disc"
6. Select Extract Entire Disc...
7. Select a new folder where you will store the game content and modify its files

Replacement of Files & Converting Extracted Game to ISO

1. Open the newly extracted folder and make any additional changes you want, such as Sonic over Yellow Android, other CharacterMods, or any other changes you want
2. Open Dolphin
3. Open Config
4. Select Paths Tab
5. Select "Add" for Game Folders
6. Navigate to the folder where you extracted the game
7. Open the sys folder, and select "Select Folder"
8. Close the confirmation pane, your games list should populate a new 0 filesize game of Shadow The Hedgehog. The 0 filesize entry is the Extracted Game format game
9. Right click the Extracted Game format game and pick Convert File...
10. The Convert window will appear, click "Convert..." and name it game.iso for Nintendont, or 2PShdTH.iso for Dolphin
11. Move/Save the ISO to the Path Dolphin detects your games. A new 2P Mod Shadow entry should appear in your Dolphins game list with greater than 0 filesize and with a custom banner. Use this when playing the game
12. If the game does not appear as you expect, in Dolphin's menu bar select View -> Purge Game List Cache

Troubleshooting / FAQ

1. Player 2 does not spawn, but a split screen appears

• You have successfully placed GUPE8P.ini as you expect, but are launching the wrong game or improperly patched the game

2. Player 2 spawns, but there is no split screen for them

• You have patched the game correctly, but GUPE8P.ini is not placed in the correct spot, or Cheats are disabled in Dolphin/Nintendont

3. I keep crashing after the Rank Screen completes on finishing a level

• If you are using a Custom BON character with the Yellow Android MTP Animation Override code, make sure you enabled the Custom MTP Crash Fix v4 code too.

4. I get Load failed. Please check the Memory Card message when loading the game

• Ensure you did not accidentally enable/check a separator in the Gecko Codes list, such as === Core Codes ===, === Gameplay Tweaks === - these are not codes, just separators and should not be enabled.
• Make sure you did not copy a Shadow SX or Shadow Reloaded save file. Only original game saves are compatible.

5. The aspect ratio switches between 4:3 and 16:9 when someone uses Chaos Control

• Ensure you are on Dolphin 2506 or newer. Pick Force 16:9, Stretch to Window, or Force 4:3.

6. My game runs at very low FPS

• This mod is very CPU intensive and requires overclocking the virtual GameCube CPU. Nintendont on Wii is the equivalent of a 150% GameCube CPU Overclock. I recommend at least matching this in Dolphin, but ultimately it depends on your own real CPU's power. See the Dolphin FPS Optimization section above.

7. I have a 16:9 monitor, and am using the widescreen version of the game, but I have black bars on the sides

• Shadow the Hedgehog and Sonic Heroes have an abnormal aspect ratio. You need to either enable Stretch to Window with Dolphin Widescreen Hack option, or enable Crop in Graphics -> Advanced if using Force 16:9 option

8. My screen explodes with weird textures everywhere

• Do not use the Dolphin Graphics Mods -> Bloom Removal feature. Instead use the included Gecko Code if you want No Bloom

9. My Wii / Wii U shuts down when loading a stage (Nintendont)

• Update your Nintendont to at least v6.503 / Apr 30 2025 20:50:09

10. Both players are being controlled by one controller

• You need to ensure the START button is not pressed at the same time on multiple controllers during stage load. In Dolphin make sure you haven't accidentally bound START to the same key/controller by mistake.

11. How do I play with others?

• This is a local splitscreen modification. Outside of playing in the same physical space, you can either use Dolphin Netplay with Dual Core OFF (it crashes with it ON), or a cloud gaming solution such as Parsec, Sunshine/Moonlight, Steam Remote Play.

12. I have texture corruption or Dolphin crashes.

• Use Vulkan Graphics backend. Do not use Direct3D 12, as it has crashing issues in Dolphin with this game. Direct3D 11 will sometimes corrupt textures (nvidia only).

13. My game crashed (PPC Halt noise) while playing on console via Nintendont

• If you travel far apart in some stages, it is still possible to exceed 24M and crash the game on console. This should be rare, but if it happens just avoid splitting up in the areas you commonly crash in.

14. My game looks stretched or squished

• Set Aspect Ratio in Dolphin -> Graphics -> Aspect Ratio to Force 16:9 or Stretch to Window if playing in Widescreen. Set it to Force 4:3 if playing in Original Aspect Ratio.

Credits

• dreamsyntax | Lead Developer | for starting this project/everything
• DonutStopGaming | Developer | major contributions to chunks, symbols, P3/AI partner mapping, Airbug, CoasterFix, GravitySwitchers, PlayerPointer, SuperShadow, structs analysis, numerous other address discoveries, and much more.
• LimblessVector for his work on identifying objects, work on the initial memory list, SinglePlayer Widescreen Hack, Stray Pixel under HP Bars fix
• TheHatedGravity for additional work on widescreen gncp patches, HD font, assistance with Models Fix project, v1.2+ MenuUI, v2.0 Banner, and a ton of testing
• Original Shadow vector used in banner by nibroc_rock (modified)
• Sewer56 for assistance brainstorming and optimizing per-splitscreen Chunk Fix V2, and all the inspiration they created
• Muzzarino for some symbol findings

Thanks

• DonutStopGaming for the many nights spent pair reversing and all the contributions to this project
• TryTwo, iwubcode, mitaclaw, JosJuice, jordan-woyak, and all Dolphin Developers for all the work they do for the Dolphin Emulator. The debugging features pioneered were essential. Without them, this mod would not be possible.
• aldelaro5 & contributors for Dolphin Memory Engine
• igorseabra4 and Sewer56 for Heroes and Shadow file reversing work & editing tools (HeroesPowerPlant, HeroesONE-Reloaded, etc...)
• LimblessVector for Shadow file reversing work (HeroesPowerPlant, DME Memory List)
• TheHatedGravity, LimblessVector, Jesus_PK, Sora, Shadowth117, DonutStopGaming, SpectralStar, MainMemory, Waddle DJ, my local friends, and all the randoms I (dreamsyntax) played with on Parsec & Sunshine/Moonlight for playtesting
• Heroes Hacking Central for keeping us insane during this project
• kotcrab for online xdelta patcher
• metaconstruct, UnclePunch, psiLupan, and DRGN of the SmashBoards / Melee Hacking Community for MCM and assistance with DOL expansion & modification
• You, for playing the game

A Notice to Modders

Anyone is free to base mods off this project. If you make a new mod based on it or create something that has 2P-ShdTH support, we would love to see it! You do not need to ask permission to make mods built off this mod or other derivative works.

Click here to learn how to build from source (not recommended for most users)