Files
smack-a-brother/README.md
T
shweet e9d8cac926 Weapons built from traits, fashion, Hourglass, About tab, and Ithaca
- Every attack is now assembled from traits on its definition instead
  of per-weapon code: an anchor and path (thrusts, out-and-back, arcs),
  shared flight physics (gravity, drag, acceleration, homing, and one
  wall response: end, burst, stick, crawl, bounce, stop, pass, return,
  latch), and flags like bouncy, drifting, tethered, orbiting, instant
  and arming. Melee are projectiles too.
- Shots have a lifetime and a fade (when damage bottoms out). Range is
  speed times lifetime. Ricochets and the Vacuum wind lifetime back.
- The Vacuum pulls anyone's shots, and its airblast flips them out
  along the aim, claiming enemies' (fading into your colour).
- New trinket: Hourglass, longer projectile lifetime and range. Ropes
  and chains lengthen with it and the Accelerator.
- Fashion: 23 items worn on the head, face or torso, chosen in Profile.
- Flamethrower flames hit continuously, the whip coils and sweeps,
  bouncing shots roll over ramps, and Ricochet relights grenade fuses.
- Profile tab, colour tooltips, option hints on every setting, an
  About tab with credits and links, and the Ithaca font.
- Loadouts lock once readied, tomatoes clear with the match, and the
  round-over pause is 4 seconds.
- CC0 license. Tools and CLAUDE.md are no longer tracked, and the web
  shell moves to web/.
2026-11-10 15:27:12 -05:00

97 lines
3.7 KiB
Markdown

# Smack a Brother
![1](/screenshots/1.png)
![2](/screenshots/2.png)
![3](/screenshots/3.png)
![4](/screenshots/4.png)
Online platform fighter. Lobbies of up to 16 players, games of up to 8. Play it in the browser [here](https://shweetz.net/smack-a-brother/).
## 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](https://emscripten.org/docs/getting_started/downloads.html).
```
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 maths 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://127.0.0.1:47800`
- `SAB_NET_LAG`: add this many milliseconds of lag
- `SAB_NET_LOSS`: drop this percent of input packets
- `SAB_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](LICENSE). 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.