A quick summary of features:
- Two layer model, with Self-like object model at the core and classes built on top.
- Very small code base (roughly 10% of the size of the GNU runtime)
- Support for @synchronized on all objects / classes.
- Support for concrete protocols / mixins.
- Support for prototype-based object orientation (can be mixed with class-based; classes really are just another kind of object in this runtime)
- Support for safe method caching (including polymorphic inline caching) with low overhead.
- Support for fast accessor methods (we can implement properties that are much faster than Apple's)