snake

A snake game in Bevy.

Run natively

cargo run                 # release-ish dev profile
cargo run --features dev  # + bevy-inspector-egui world inspector

Platform backends (X11/Wayland/WebGL2) are all in one feature list in Cargo.toml - each is inert on the platforms it does not apply to, since winit and wgpu gate them by target cfg - so neither command needs a --features flag.

Build for the web

./build-wasm.sh
python3 -m http.server -d web    # then open http://localhost:8000

Needs the nightly toolchain (see rust-toolchain.toml), the wasm32-unknown-unknown target, wasm-bindgen-cli matching the wasm-bindgen version in Cargo.lock, and wasm-opt (binaryen).

Iterating on the game? FAST=1 ./build-wasm.sh skips the std rebuild, LTO and wasm-opt, which turns a ~2.5 min rebuild into ~5 s at the cost of a much bigger binary. Drop the flag for anything you ship.

CONVERGE=1 spends extra wasm-opt passes for a last ~1-2%.

Shipping builds keep Bevy's logging and panic messages, so the browser console names a failure instead of trapping on unreachable. That costs ~237 KB brotli and is worth it: a silent build cost three debugging round trips once already. All paths in those strings are trimmed by trim-paths = "all" in [profile.wasm-release], so they read bevy_render-0.19.0/src/... and no $CARGO_HOME or $HOME layout ships.

The renderer is WebGL2. WebGPU builds are ~790 KB smaller but have no fallback: a browser that exposes navigator.gpu while requestAdapter() resolves to null - Linux Chromium and Firefox today - fails with "No available adapters" and a blank canvas, and wgpu picks its backend from navigator.gpu alone, so compiling both backends does not save it.

How the binary is kept small

lever	where
Only the needed Bevy features (no audio/3D/glTF/animation/scenes/picking/gizmos/reflection registry)	Cargo.toml
World inspector, its reflection registry and the only egui dependency behind an off-by-default dev feature	Cargo.toml, src/main.rs
No egui: the menu/game-over screens are bevy_ui + bevy_text, whose default_font is an 18 KB built-in subset	Cargo.toml, src/main.rs
opt-level = "z", fat LTO, one codegen unit, panic = "abort", symbols stripped	[profile.wasm-release]
No panic locations (-Zlocation-detail=none via rustflags)	[profile.wasm-release]
wasm-opt -Oz, name/producers/debug sections removed	build-wasm.sh

Serve the .wasm with Content-Encoding: br (or gzip) - it compresses about 5:1.