Could be fun :)

But note that on the Lisp Machine/Genera, every type has a presentation and can be “printed” to the REPL. This includes any new classes that you create as part of your own programs. It’s not just a small list of standard types, but every type.

The standard tutorial for the system is to implement Conway’s Game of Life. It has you create a class to hold the game board and then guides you through the process of defining a presentation for it so that the it can be displayed easily.