The PostScript language itself is quite fascinating.
Yesterday’s NeWS
Slava Pestov

Here’s a visual interface to NeWS PostScript:
The PSIBER Space Deck is an interactive visual user interface to a graphical programming environment, the NeWS window system. It lets you display, manipulate, and navigate the data structures, programs, and processes living in the virtual memory space of NeWS. It is useful as a debugging tool, and as a hands on way to learn about programming in PostScript and NeWS.