Update README and write some light docs

README.md

@@ -1,11 +1,27 @@
 # jolt-rust
-Rust bindings for [Jolt Physics](https://github.com/jrouwe/JoltPhysics) using [JoltC](https://github.com/SecondHalfGames/JoltC).
+Rust bindings for [Jolt Physics](https://github.com/jrouwe/JoltPhysics) 5.0.0 using [JoltC].
 
-Early work in progress.
+This project is an early work in progress. Watch for exposed nails.
 
 ## Goals
-1. Functioning, up-to-date unsafe wrapper for Jolt Physics
-2. *Eventually*: A safe wrapper for Jolt Physics
+1. `jolt-sys`: Functioning, up-to-date unsafe bindings to Jolt Physics
+2. `jolt`: Ergonomic, safe bindings to Jolt Physics
+
+## Crates
+
+### `jolt-sys` — Jolt bindings via [JoltC]
+This crate contains unsafe bindings to JoltC.
+
+### `jolt` — aspirationally safe Rust Jolt bindings
+This crate contains a higher-level wrapper around JoltC, providing ergonomics comparable to using Jolt from C++.
+
+The safety of this crate is currently provided on a best-effort basis.
+
+### `hello-world-sys` — HelloWorld using `jolt-sys`
+This is a port of Jolt's [HelloWorld] example to Rust using `jolt-sys`. It isn't pretty nor safe, but it does have identical behavior.
+
+### `hello-world` — HelloWorld using `jolt`
+This is a port of Jolt's [HelloWorld] example to Rust using the `jolt` crate. The goal of this example is to replicate the behavior of the original example entirely in safe Rust.
 
 ## License
 Licensed under either of
@@ -16,4 +32,7 @@ Licensed under either of
 at your option.
 
 ### Contribution
-Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.
+Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.
+
+[JoltC]: https://github.com/SecondHalfGames/JoltC
+[HelloWorld]: https://github.com/jrouwe/JoltPhysics/blob/master/HelloWorld/HelloWorld.cpp