Project Tandem

Project Tandem — Mario Kart: Double Dash!! Online on PC

Play Mario Kart: Double Dash!! online with friends on Windows. Project Tandem is a native PC port and static recompilation project for the GameCube game, with 2–8 player online multiplayer, solo or shared karts, natural widescreen, modern controllers, and automatic menu/racing mouse and keyboard controls.

Download Public Beta 3 for Windows (experimental display features) · Installation and updates · Controls · Online play

Bring your own compatible disc image. Project Tandem verifies your USA GM4E01 ISO/CISO and recompiles the game on your PC. Downloads contain the recompiler, runtime, project features, and installation tools. They do not include a disc image or a compiled copy of the game.

Beta 3 fixes dropped native fallback frames when interpolation is enabled. VSync and interpolation remain experimental, independent and OFF by default in F1 → Display. Output rate still depends on the scene and PC. Changes and testing · Display options and limits · Previous Beta 2

Features

• Mouse and keyboard menus, separate racing controls. Click through the offline and online menus, type names and room codes, then enter a race with a dedicated driving layout. The controls switch automatically. Race bindings stay active through race results and the award ceremony, and can be rebound in F1.
• Switch between mouse/keyboard and controller. Player one accepts both by default: use a mouse in the lobby and pick up a controller to drive. F1 also supports explicit device assignments.
• Online play for 2–8 people. Host a room and share its eight-character code. Take an empty kart or join a friend's back seat. Solo and shared karts can race together.
• Grand Prix and Battle. Play a cup with CPUs filling Grand Prix slots, or compete in Balloon Battle, Shine Thief, and Bob-omb Blast. Battle requires at least two opposing karts.
• Shared character selection. Everyone sees live player markers and named, locked choices on the original character grid, with their own kart preview below. Solo players choose two characters; shared teammates choose one each.
• Stay together between events. Return to the same lobby, change seats and modes, edit your name, and keep session medal stars.
• Natural 16:9 widescreen. See more of the course with correctly proportioned HUD elements. Choose common 16:9 resolutions, windowed mode, fullscreen, or borderless fullscreen.
• Controller and local multiplayer settings. Xbox, PlayStation, and Switch controller support through SDL, rebindable controls, and separate device assignments for offline GameCube ports.
• Online prediction and adaptive buffering. Peer-to-peer gameplay uses EOS connection setup and relay fallback. The F10 overlay shows FPS, RTT, and the current input buffer. Performance depends on the PCs and connection.
• Portable setup and updates. Compiler tools are bundled. Update by copying the full patch ZIP over your existing folder while preserving local-data.

Install on Windows

1. Open Releases and download the Windows full package. GitHub's automatic Source code archives are for development, not the player installer.
2. Extract the ZIP completely into a writable folder.
3. Run Setup-Tandem.cmd and select your own supported USA ISO/CISO.
4. Allow setup to verify the disc and compile locally, then run Launch-Tandem.cmd.

The player package includes its build tools. You do not need Visual Studio, a separate Windows SDK, or Python installation. Online players do not need an Epic player account or developer setup. Ordinary home connections use automatic connection setup and relay fallback without a VPN or manual port forwarding; restrictive networks can still prevent a connection.

Requirements: 64-bit Windows 10 or 11, graphics supporting desktop OpenGL 3.3, a writable installation folder, and space for the toolchain, build output, and a private cached copy of your ISO. This beta targets Windows x64.

The supported disc is USA GM4E01, with main.dol SHA-1 e389e50357d4a5076ab3d38672204658f411123d. Setup rejects an incompatible revision. Other regions and RVZ/GCZ input are not supported by this installer.

Installation and updates · Controls · Online play · Troubleshooting

Mouse and keyboard controls

Menus

Input	Action
Mouse	Point at and highlight a menu choice
Left click	Select or confirm
Right click or Escape	Go back; confirmation appears when leaving a lobby
Arrow keys	Navigate
Enter	Confirm
Backspace	Go back
Typing	Enter your name or room code in an active text field
F1	Open settings

Mouse clicks also advance the introductions and the initial save prompt. Menu controls change automatically when racing begins; no manual profile switch is needed.

Racing

Input	GameCube action
Left click	A — accelerate
Right click	B — brake/reverse
A / D	Main stick left/right — steer
W / S	Main stick up/down
Space	X — use item
Q	Y — use/pass item
E	Z — switch riders
Left Shift	R trigger — drift
Ctrl	L trigger
Arrow keys	D-pad
Enter or Escape	Pause offline / open the online menu

Race bindings remain active between races and through the award ceremony: left click confirms those screens. Arrow keys navigate result/pause choices and Enter confirms. F1 settings remain available, and all race bindings can be changed there.

Player one can use a controller at any time alongside mouse/keyboard unless you explicitly assign devices in F1. Xbox defaults keep A/B/X/Y matched to their labels, RB is Z, and Menu is Start. Other controller layouts can be customized in F1.

Play with friends

Choose Online Play → Host Room and share the room code, or join using Join Room or F1 → Online → Quick join. Pick seats, ready up, and let the host choose the mode. All players need the same version and build ID, shown in the lobby and settings.

Current compatibility: Public Beta 3 — f4e52689263937fd, based on Alpha25 gameplay. Everyone must update to the same build; Older builds cannot share a room with Beta 3. Display option choices may differ between players.

Use F1 → Exit to desktop, the window close button, or Alt+F4 to exit. Online services close automatically with the game.

Updates and support

Close Tandem, copy all files from the cumulative update ZIP into the folder containing Launch-Tandem.cmd, and accept replacement. Keep local-data. The launcher rebuilds when needed. The cumulative package supports portable installations from Alpha12 onward.

Report problems through this repository's Issues, using the bug-report form. Include the version/build ID, Windows version, player count, mode, and steps to reproduce. For network problems, include each player's FPS/RTT/BUF readings. Share only reviewed diagnostic excerpts; the troubleshooting guide explains which files to keep private.

Source and credits

Project Tandem builds on Ethan Nicholas's mariokartdd-recomp and gcn-recomp. The runtime statically translates PowerPC code from the user's disc image to C and compiles it locally.

Project source uses the MIT License. Third-party libraries, fonts, artwork, and distributed runtime components have separate notices; see credits, third-party notices, end-user terms, and privacy information. The MIT license does not license Nintendo's game content or trademarks.

Mario Kart: Double Dash!!, GameCube, characters, and related marks belong to their respective owners. Project Tandem is an independent project and is not affiliated with or endorsed by Nintendo or Epic Games.