Multiplayer Everything

Multiplayer Everything makes multiplayer mods for games that never had multiplayer before. Open the launcher, pick a game, and press Play online. For the Flash games it starts them in Ruffle Together (our Ruffle build with online co-op) with the right file and settings, and you join a room with a code: no IP addresses, no port forwarding. For the PC game mods (Spooky Together, Baldi Together, MiSide Together, CupHeads, Rick and Morty Together, Dave the Diver Multiplayer and more) it finds your copy of the game, installs the mod into it, keeps it up to date, and can take it out again, putting back every game file it replaced. Native C++20/Win32, no dependencies, and the whole app is one .exe.

Questions, bugs, or looking for people to play with? Join the Multiplayer Everything Discord.

Games available now: Gun Mayhem 2 · Stealth Hunter 2 · Bad Ice-Cream · Territory War · Bow Man · Ultimate Crab Battle · Air Battle · Raft Wars · PC mods: Spooky Together · Baldi Together · MiSide Together · CupHeads · Rick and Morty Together · Dave the Diver Multiplayer · GTA San Andreas Co-op. The sidebar keeps PC mods and Flash mods apart. Full list under Games.

Quick start

1. Download MultiplayerEverythingLauncher.exe from Releases (or the .zip with the editable launcher.json and covers next to it) and put it in its own folder: game files are saved in a games\ folder beside it.
2. Run it. If Ruffle Together is not found it offers to install it; say yes.
3. Set your name in Settings once (Ctrl+,).
4. Flash game: select it and press Play online, or Quick play to join the busiest open room. PC mod: select it and press Install, then Launch.

More detail: Playing a Flash game and PC game mods.

How it works

	Flash games	PC game mods
What the launcher does	Finds Ruffle Together and the game's .swf, builds the exact command line, starts it, watches it exit	Finds the game, downloads the mod's package, installs it into the game's folder, keeps it updated
Online play	Rooms with a code on the central server; direct IP through the built-in relay (Radmin, LAN, Tailscale)	The mod connects through the same central server
Safety	Checksums on every download (Ruffle Together, game files, the launcher itself)	One all-or-nothing install with a SHA-256 check; backups of replaced files; Uninstall restores the game
Where it's configured	launcher/launcher.json	the game's mod object in launcher/launcher.json
Guide	CONFIG.md	docs/MOD_PACKAGES.md

A new game or mod never needs a code change: everything lives in launcher.json (also built into the exe, so the exe is all you need to send someone).

What it does

• Installs PC game mods safely. Pick a mod, press Install: the launcher finds the game (Steam, Epic, registry, or a folder you choose), downloads the mod's package, checks it against its SHA-256 and copies it in as one all-or-nothing transaction. Cancel, an error or a crash undoes every change; files the mod replaces are backed up first; your edited settings files are kept on update. Update, Repair and Uninstall work the same way, and a mod installed earlier by its stand-alone setup is recognised as installed. Mods are installed per game and need the game closed.

• Finds everything itself. Ruffle Together (its own players\ruffle-together\ folder) and each game's .swf in games\ or your Flashpoint folder. Anything missing gets a button that fixes it: Locate game file... or Install Ruffle Together.

• Installs Ruffle Together for you. Without it, the launcher offers to install it: it downloads the newest release from our ruffle-coop GitHub page, checks it against the published SHA-256 checksum, and unpacks it into players\ruffle-together\. Nothing is downloaded without your OK.

• Player slots. Every game shows how many players it takes, in the players' own colors (P1 red, P2 blue, P3 green, P4 yellow). While you host, the slots fill with the names of the people who joined.

• Online first. Online games lead with Play online: rooms with a code on the Multiplayer Everything central server, no IP addresses and no port forwarding. Quick play joins the busiest open room, or starts the game ready to host when none is open. Direct IP (Radmin, LAN) is still there under Other ways to connect.

• A lobby for the games. For mods made for it, Play online opens the launcher's own lobby: host a room (on the server or by direct IP, with an optional password) or join one, see who's in it in their P1-P4 colors, chat, and press I'm ready. The host presses Start game and every launcher opens the game with the room's values; the game starts only once everyone's game has loaded. Dropped players get 30 seconds to come back to their slot, the host can kick or ban, and direct-IP hosts get their addresses (VPNs first), a firewall check, a port test and optional UPnP. The mod itself needs no online panel: it talks to the launcher on 127.0.0.1 (docs/LOBBY_BRIDGE.md).

Games

Game	Actions	Notes
Gun Mayhem 2: More Mayhem	Play online, Quick play, Play on one keyboard	Up to 4 players, with the Gun Mayhem 2 Online mod. Direct IP: relay port 7777.
Stealth Hunter 2	Play online, Quick play, Play solo	The Stealth Hunter 2 Online mod adds co-op for up to 4. Runs in Ruffle only. Direct IP: relay port 7778.
Bad Ice-Cream	Play online, Quick play, Play on one keyboard	Two players, with the Bad Ice-Cream Online mod (Nitrome's game).
Territory War	Play online, Quick play	Red against blue on up to 4 PCs.
Bow Man	Play online, Quick play	Two archers on two PCs. Ruffle only.
Ultimate Crab Battle	Play online, Quick play	Co-op for up to 4, one ship each.
Air Battle	Play online, Quick play	Co-op for up to 4, one balloon boat each.
Raft Wars	Play online, Quick play	Co-op for up to 4, taking turns at the bazooka.
Intrusion, Intrusion 2		Coming soon: listed, no buttons yet.

The newer mods are online-only (no direct IP); their single-player modes are under Play offline when Settings shows offline play. Until a mod's file is published in mods-info, the central server doesn't know the game: its card says Not on the server yet and Quick play is hidden.

More games are on the way; the local-only classics (Gun Mayhem, Fireboy and Watergirl, Boxhead) are set aside in docs/local-games-example.jsonc for now.

The original, unmodded versions of the modded games are hidden; Settings can show them (Play the original).

Getting the games. When a game file is missing, the game shows Download game files: the launcher fetches them from multiplayereverything/flash-games, checks each file against the SHA-256 in that repository's catalog, and saves it in games\. That covers every game in the list except the coming-soon ones (the repository's README lists how far each build is tested). You can also put your own .swf files in games\ (names are in games\README.txt), use Locate game file..., or install Flashpoint, whose copies are picked up automatically.

PC game mods

Not Flash: installed into the game's own folder.

Mod	Game	Notes
Spooky Together	Spooky's Jump Scare Mansion: HD Renovation (Steam)	Co-op for 2 to 4 players. Installs the mod from the newest release of spooky-together, together with the BepInEx 5 loader published in the same repository.
Baldi Together	Baldi's Basics Plus (Steam)	Co-op for 2 to 4 players, over LAN or Steam. Installs the mod from baldi-plus-coop, together with the BepInEx 5.4.23.5 loader published in the same repository.
MiSide Together	MiSide (Steam)	Co-op for 2 to 4 players, through Steam, LAN or an address. Installs the mod from miside-coop, together with the BepInEx 6 (IL2CPP, be.790) loader it needs, which is published in that repository's releases.
CupHeads	Cuphead (Steam)	Online co-op for 2 players over Steam invites or LAN, from CupHeads (a fork of Germanized's CupHeads). Installs the mod and the BepInEx 5.4.23.5 loader published in that repository.
Rick and Morty Together	Rick and Morty: Virtual Rick-ality (Steam, VR)	Co-op for 2 players, from rick-and-morty-coop. Installs the mod, its BepInEx settings (this game needs them) and the BepInEx 5.4.23.5 loader from the same repository.
Dave the Diver Multiplayer	DAVE THE DIVER (Steam)	Two-player co-op through Steam or LAN, from Dave-The-Divers-Coop (a fork of S1ii's Coop-Divers). Installs the mod and the BepInEx 6 (IL2CPP, be.790) loader published in that repository.

| GTA San Andreas Co-op | Grand Theft Auto: San Andreas, PC version 1.0 US (Steam or Rockstar) | Co-op for 2 to 4 players, based on CoopAndreas, from gta-coop. Does what the mod's own install.bat does without running it: keeps the game's eax.dll as eax_orig.dll, puts the co-op eax.dll in its place, and Uninstall puts the original back. The host's server is installed under CoopAndreas\server. You need your own copy, downgraded to 1.0. |

Each is downloaded from its GitHub release, checked against the SHA-256 GitHub publishes for it, and installed as one all-or-nothing change; Uninstall puts the game folder back exactly as it was. How a mod is described: docs/MOD_PACKAGES.md.

Pick the mod, press Install, then Launch. Update, Repair and Uninstall sit beside it; the game must be closed. Try it safely from the command line with --game-dir on a copy of the game folder. Authors: see docs/MOD_PACKAGES.md.

Playing a Flash game

Hosting: set your name in Settings once. Select the game, press Play online, then in the game press F9, set MODE to ONLINE and click HOST. Send friends the room code it shows; the room also appears in everyone's Rooms list.

Joining: pick the room on the Rooms page or the game's Rooms tab and press Join (or type the code under Join by code). The code is on your clipboard: in the game press F9, paste it and click JOIN, if the game hasn't joined by itself.

Direct IP (Other ways to connect): Host with your IP starts the built-in relay and shows the addresses friends type, including Radmin VPN, ZeroTier or Tailscale. Windows may ask to allow MultiplayerEverythingLauncher.exe through the firewall the first time: allow it, or friends can't connect.

Keyboard: arrow keys move through the grid, Enter plays, Ctrl+F searches, Ctrl+, opens Settings, F5 rescans for players and game files, Tab reaches every button.

Command line

MultiplayerEverythingLauncher.exe --list                       every game and whether it can start
MultiplayerEverythingLauncher.exe --launch gunmayhem2:host     start an action without the window
MultiplayerEverythingLauncher.exe --relay 7777                 run only the relay (a dedicated relay PC)
MultiplayerEverythingLauncher.exe --install-player ruffle      install Ruffle into players\ruffle
MultiplayerEverythingLauncher.exe --download-game all          download every game file the catalog has
MultiplayerEverythingLauncher.exe --rooms gunmayhem2           list the open rooms on the central server
MultiplayerEverythingLauncher.exe --update                     install the newest launcher release now
MultiplayerEverythingLauncher.exe --mods                       the PC mods: game found, installed version, newest version
MultiplayerEverythingLauncher.exe --install-mod spooky-together  install or update a PC mod (add --game-dir "<folder>" to point at the game)
MultiplayerEverythingLauncher.exe --repair-mod spooky-together   put back missing or damaged files
MultiplayerEverythingLauncher.exe --uninstall-mod spooky-together  remove it and restore the game's files
MultiplayerEverythingLauncher.exe --validate                   check launcher.json

MultiplayerEverythingLauncher.exe --help lists everything. Settings and the log live in %LOCALAPPDATA%\MultiplayerEverything\FlashLauncher\.

Build

Requires Visual Studio 2022 (or Build Tools) with the C++ workload.

powershell -ExecutionPolicy Bypass -File build.ps1 -Test
powershell -ExecutionPolicy Bypass -File build.ps1 -Dist

-Test runs the C++ tests (config, file lookup, command lines, settings, and the relay against real sockets) and tests\e2e.ps1, which drives the real exe and its window through the accessibility API with a fake player, and installs a fake player and fake game files from a local test server (checksums, failed reinstall, first-run prompt, the window's download button). -Dist makes dist\MultiplayerEverythingLauncher\ and its .zip, and refuses to package any .swf or player binary; it also copies the single-file dist\MultiplayerEverythingLauncher.exe.

Repository

Path	Contents
src/core/mod/	The PC-mod engine (ported from the installer template): game detection, planning, the all-or-nothing install transaction, the install record, package download
src/core/lobby.*	The lobby: rooms through the server or direct IP, ready-up, start and the loaded barrier, reconnects, and the localhost bridge the game talks to
src/core/	No UI: config, library (players, files, command lines), process watching, relay, downloads, rooms, settings, Discord, built-in files
src/ui/	The launcher window and its theme
src/app/	Entry point and command line
launcher/	launcher.json and covers\ (both also built into the exe), games\, players\
docs/ADDING_A_MOD.md	Checklist for adding a PC mod: author, review, loader, entry, tests
docs/html5-example.jsonc	HTML5 support (browser players, Plazma Burst 2 co-op), kept out of the shipped list for now
docs/local-games-example.jsonc	Gun Mayhem, Fireboy and Watergirl, Boxhead: local-only games set aside for now
tests/	C++ tests and the end-to-end script
CONFIG.md	Every launcher.json option

Ruffle Together is built from Ruffle, which is open source (ruffle.rs). The games belong to their owners; this project ships neither the player nor any game.

Made with

This project was made with the help of these tools:

• antislop-ui
• coop-anything
• REA
• Universal Modder