In 1997 I retrieved Plumbin' from an old Tektronix 4404 that had been collecting dust in the basement. I loaded it into Squeak Smalltalk and got all the graphics converted to color. Oooh.
Revived version uses Squeak's color interface.
I added an infinite recursion check. Plumbin' was originally written for a dialect that could only allocate 32 thousand objects. If you assembled a loop of pipes the simple simulator would loop too and quickly exhaust all but a small reserve of the object space -- just enough to bring up a notifier. I thought this behaviour to be quite sophisticated and loved to show it off. Now an infinite loop just drives Smalltalk into paging so I have to explicitly check for loops and issue my own notice.