Rengo

I recently learned of the Go board game. In case you are not familiar with the game, you have probably heard of it before when AlphaGo beat its best player. I desired a four player implementation that was playable from a web browser.

Around the same time, I came across Pont, an implementation of another board game that used Rust for both the server and client. The server is multithreaded with an asynchronous runtime, and exposes a WebSocket API that a client can interface with. The client was written with a Rust to JavaScript transpiler / Rust to WebAssembly compiler. I decided to wrte my Go stack in Rust, similar to what was done with Pont.

Rengo is a four player implementation of Go that does not alter the game logic. Rather, two people on a single team take turns playing against another team of two. This preserves the two team, turn based gameplay. This is the game that I implemented. I spent some time familiarizing myself with the crates that were used in Pont.

For the frontend, I used wasm-bindgen, js-sys, and web_sys. I wrote a substantial amount of code that used functionality from web_sys. It provides a Rust interface to many of the common JavaScript functions that are necessary to create an interactive WebSocket game. For example, the crate enables the rendering of a canvas element, and dynamic resizing of site elements and fonts. I used Bootstrap 4.5 to style the page. One problem I had when utilizing Bootstrap modals to notify the user was that I had to call a function through JQuery to show the modal. js-sys allowed me to define a function prototype to call the JQuery function.

For the backend, I used the same crates that Pont used. Namely, I used smol as the asynchronous runtime, async-tungstenite as an asynchronous WebSocket listener, and bincode for binary data serialization to transmit Rust enums across WebSocket. The server was generally straightforward. The server allows for creation of rooms, where a player capacity can be specified. Rooms follow an actor model, where the connection handler messages a room to request an action.

A good amount of boilerplate code was written. Actix could be used to elegantly setup an actor based concurrency model. The client code contains some weird code, such as this line

ctx.fill_text(&format!("{}", i as u32 + 1), inner_begin + inner_size
+ 5_f64 * inner_begin / 9_f64 - font_size as f64 / 3_f64, inner_begin +
line_space * i as f64 + 8_f64 * font_size as f64 / 20_f64)?;

which is needed to properly align letters on the game board. After writing Rengo, I discovered yew, which is a framework for writing interactive web applications in Rust. It uses some macro generated syntax that functions similarly to JSX.

I am enjoying both Rust and Go quite a bit. An idea that I have had is to write a more general and polished Go platform that takes advantage of existing frameworks such as Actix and yew. If you are interested in Go, make sure to try OGS, which is a great Go web service for playing games against player and bots, with built in game analysis.