Cuis is a free Smalltalk-80 environment that aims to be simple and powerful. It is praised by experts like Dan Ingalls, Alan Kay, and John Maloney for its malleable software and clever design. The latest updates include the addition of presentations and papers to the documentation, the porting of the Dr. Geo interactive geometry application to Cuis, and the enabling of Unicode by default for all source code and text files. The Cuis Book has also been updated for the latest version, and Cuis 6 has been recently released.
https://cuis.st/