I wish someone would try to reimplement Symbolics Genera under an open source license and make it run on modern hardware properly, without VLM. Its design and philosophy is quite different from Unix derivatives, being so object-oriented in the right parts and extensible on the source code level. The user interface was very reminiscent of the notebook interface in Mathematica - output in the listener wasn't plain text as in Unix CLI, but arbitrary objects like bitmaps or graphs or interactive widgets. You could click on any of them and inspect its state or open the source file that implements it.