Small World is not a true Smalltalk-80 system. The language is slightly smaller, the standard library is distinctly smaller, but nonetheless it tries to preserve the look and feel of Smalltalk-80. These features include a dynamically typed and interpreted langauge, a certain feel to the syntax, and a highly interactive and totally reflective programming environment.
In the case of SmallWorld, this is all achieved with a virtual machine that is approximately 1200 lines of Java (two thirds of which are devoted to primitive methods) and about forty classes in the standard image.
So enjoy. As I find time I'll try to improve the documentation on the system, but the best documentation is the code itself.