sporksmith/snake-wasm4

Built following the wasm-4 snake tutorial, in zig.

See also https://github.com/christopher-kleine/wasm-4-tutorial-games for the tutorial author' alternate implementations in zig and other languages.

Play now

https://sporksmith.github.io/snake-wasm4/

Running locally

Build:

$ zig version
0.9.0
$ zig build

Play locally (requires w4):

$ w4 -V
2.0.0
$ w4 run zig-out/lib/cart.wasm

You can also play in w4's wasm engine instead of a browser. For me this fails mysteriously on debug builds (but works when compiling with e.g. -Drelease-small=true).

$ w4 run-native zig-out/lib/cart.wasm

Interesting bits beyond the tutorial

• log in main.zig is a callback for std/log.zig, and wires up the standard library's logging to the one provided by wasm4 (trace). It uses a fixed size stack-based buffer to format log strings.

• panic in main.zig is a callback for std/builtin.zig, and overrides the default panic handler. It logs the panic message before calling the default handler (which doesn't).

Thoughts

I'm new to zig, wasm, and wasm4, so this is mostly just a learning exercise.

While zig's error reporting for undefined behavior in debug builds is pretty good normally, I haven't been able to get anything useful in this environment. Pretty much just line 1 > WebAssembly.instantiate:2930.

Other than that I had fun playing with zig, and appreciated the control over memory for this kind of constrained environment. I had fun playing a bit with compile-time logic while writing a logging hook that works without a heap. (I know I could've wired up a standard allocator to a fixed-size buffer, but I wanted to control memory usage more tightly)