Not intended to merge in its current state. Just creating this PR for discussion purposes.

Used https://rustwasm.github.io/book/reference/code-size.html for some guidance. In particular this poitned me toward wasm-snip. I used it here to snip out panic code, which is probably what we'd want in most cases, and also to strip out formatting code. The latter is a bit more aggressive and could break things if the game is using Rust's string formatting other than in panics.

Un-post-processed release build on main: ~140 KB

$ cargo build --release
$ ls -go target/wasm32-unknown-unknown/release/*.wasm
-rwxrwxr-x 2 140570 Jan  2 09:26 target/wasm32-unknown-unknown/release/snake_w4_rs.wasm

wasm-opt only on main: ~99 KB

$ cargo build --release
$ wasm-opt -Oz --strip-producers --dce --zero-filled-memory target/wasm32-unknown-unknown/release/*.wasm -o optimized.wasm
$ ls -go optimized.wasm 
-rwxrwxr-x 1 99304 Jan  2 09:30 optimized.wasm

wasm-opt + wasm-strip (strips out debug info) on main (EDIT: you can also just add the --strip-debug flag when calling wasm-opt): ~22 KB

$ cargo build --release
$ wasm-opt -Oz --strip-producers --dce --zero-filled-memory target/wasm32-unknown-unknown/release/*.wasm -o optimized.wasm
$ wasm-strip optimized.wasm
$ ls -go optimized.wasm 
-rwxrwxr-x 1 22562 Jan  2 09:31 optimized.wasm

wasm-opt + wasm-strip + wasm-snip on main: ~13 KB

$ cargo build --release
$ cp target/wasm32-unknown-unknown/release/*.wasm optimized.wasm
$ wasm-snip --snip-rust-fmt-code --snip-rust-panicking-code -o optimized.wasm optimized.wasm
$ wasm-strip optimized.wasm
$ wasm-opt -Oz --strip-producers --dce --zero-filled-memory optimized.wasm -o optimized.wasm
$ ls -go optimized.wasm 
-rwxrwxr-x 1 12887 Jan  2 09:35 optimized.wasm

wasm-opt + wasm-strip + wasm-snip + remove usage of Mutex and lazy_static: ~7 KB

$ ./build.sh
$ ls -go optimized.wasm 
-rwxrwxr-x 1 6876 Jan  2 09:36 optimized.wasm

Added an example of how to make a simple 2D platformer game for WASM-4.

There are many ways of doing a platformer. This one evolved from the Maze example and uses bounding boxes to check all the collisions.

Platformers are one of the very first things people want to make once they get introduced to a new engine or platform. That said, an example like this can be extremely valuable to introduce people to WASM-4 and serve as a base for people to use and evolve from it.

$ cargo clippy
warning: called `is_some()` after searching an `Iterator` with `find`
  --> src/snake.rs:98:18
   |
98 |                   .find(|&body_section| body_section == first)
   |  __________________^
99 | |                 .is_some(),
   | |__________________________^ help: use `any()` instead: `any(|body_section| body_section == first)`
   |
   = note: `#[warn(clippy::search_is_some)]` on by default
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#search_is_some

• https://rust-lang.github.io/rust-clippy/master/index.html#search_is_some

Tried to keep it as direct a port as possible but it necessitated a few support functions, snake_create and snake_push. The rest is almost a literal port.

Replaced include guard with #pragma once for brevity.

Removed malloc to simplify snake_create and remove non-portable code.

Replaced struct assignment with field assignment for clarity.

There were a few complaints about the file size of the Rust Snake example (~141KB; ~100KB with wasm-opt).

Some possible issues for this are:

• Use of external crates (lazy-static and fastrand) may contribute to the overall size.
• Idiomatic Rust could be adding too much bloat into the code and may not be the best choice for keeping a balance between size optimization and easy-to-understand code.

I decided to rewrite everything and see if I could provide an example which would output a smaller file size while still being easy to explain to a beginner. The following changes were made:

• lazy-static was removed in favour of using static mut.
• fastrand was removed in favor of a simple rand() function using Xorshift algorithm.
• Everything is now part of one single lib.rs file.
• Code is almost fully documented.

There are still a few things to fix:

• Improve source code formatting.
• Re-split each section into separate files if needed.
• Comment the remaining parts of code.
• Resolve some TODOs left in the code.

With all these changes, Rust Snake now only has ~72KB of file size (~10KB with wasm-opt).