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- Lobbies: a name (default "Lobby <code>"), Unlisted or Public, and an optional password. The Multiplayer page scrolls: a Browser of public lobbies (name, count, padlock, code, little player previews, Join with a password field when locked), Join by code, Create, then Settings. Errors show under whatever caused them. Links take ?pass= (and --pass), and Copy Link includes it. Protocol 11. - Queue areas center on their host along the floor's flat stretch, squeezing their slots to fit, and move to a nearby surface when the host's is too short. - An airblast steals an enemy's flail ball onto its own chain for a while. Flail balls reel themselves back after 15 seconds. Doubler echoes of the Grimoire teleport move you too. - The Good Stuff: a new trinket, the inverse of Diazepam (more spread). Spread is now a multiplier, and it widens or narrows the Vacuum's cone. - Balance: Sword basic slash 25% smaller and charged slash half the size, Whip basic lash half the damage and reach, Recoil Coil recoil halved, Speedometer no longer speeds you up. - Fixes: fashions survive coming back from a game, Quit shows only in the sandbox menu, and the chat log keeps above the menu's tip.
Smack a Brother
Online platform fighter. Lobbies of up to 16 players, games of up to 8. Play it in the browser here.
Clarification
This application was developed with the assistance of a large language model.
Build
After cloning and entering the repository's directory, make sure to initialize the submodules:
git submodule update --init --recursive
Everything (SDL, libdatachannel, simdjson) is built statically from the submodules. The game's resources are in resources/ and get linked next to the executable.
Linux
Needs OpenSSL, plus the X11/Wayland and audio headers SDL builds against.
mkdir build
cd build
cmake ..
make
Web
Needs the Emscripten SDK.
emcmake cmake -B build-web -DCMAKE_BUILD_TYPE=Release
cmake --build build-web
This makes smack-a-brother.html, .js, .wasm and .data. Rename the .html to index.html and serve all four.
Server
The server builds on its own, without SDL. It needs OpenSSL (libssl-dev on Debian).
cmake -S server -B build-server -DCMAKE_BUILD_TYPE=Release
cmake --build build-server
Run it with:
smack-a-brother-server [port] [first UDP port] [last UDP port]
Defaults are 47800, 47810 and 47899. It only listens on 127.0.0.1, so put it behind a reverse proxy that handles TLS. For nginx:
location /smack-a-brother/ws {
proxy_pass http://127.0.0.1:47800;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
proxy_set_header Host $host;
proxy_read_timeout 120s;
}
Open the UDP range in the firewall (e.g. ufw allow 47810:47899/udp).
Netcode
- The server runs every lobby: a sandbox everyone in the lobby shares, plus the games queued in it. Each is its own simulation. All of them run on one thread, at 60 ticks a second.
- Clients send their inputs ahead of time. Each tick the server takes what has arrived (repeating a player's last inputs if they're late), steps the simulation, and sends everyone the inputs it used. Every 60 ticks it also sends a checksum.
- Clients run the same simulation about 3 ticks ahead of the server, guessing other players' inputs. When the server's inputs differ from the guess, the client rolls back and replays.
- The simulation is deterministic on every platform (strict floating point, own math functions), so desktop and web play together.
- Clients connect over a WebSocket first (lobbies, chat, WebRTC signaling). Then they open a WebRTC connection to the server with two data channels: a reliable one, and an unreliable one for inputs and frames. If WebRTC can't connect, everything stays on the WebSocket.
- STUN:
stun.l.google.com:19302. - The server address is set in Settings. Default:
wss://shweetz.net/smack-a-brother/ws.
Joining a lobby directly
- Desktop:
smack-a-brother --join CODE - Web:
https://shweetz.net/smack-a-brother/?lobby=CODE
Environment variables
SAB_SERVER_URL: use a different server, e.g.ws://127.0.0.1:47800SAB_NET_LAG: add this many milliseconds of lagSAB_NET_LOSS: drop this percent of input packetsSAB_NET_STATS: log how the client is keeping up with the server
License
The game's code and art are released into the public domain under CC0 1.0. Not covered by that: the Ithaca font (SIL Open Font License, see resources/font/LICENSE.txt), the sound effects cut from the Sound Ideas libraries (see resources/sfx/SOURCES.md), and the libraries in external/, each under its own license.