Type "open mailbox" in The Visible Zorker, and the game does what it always did: tells you the mailbox is open, with a leaflet inside. But on the same page, you also see the function that just ran, what variables it touched, and where every object in the room currently sits. Andrew Plotkin, the interactive fiction veteran behind the Obsessively Complete Infocom Catalog, has turned Zork into an explorable exhibit where the parser does its work in front of you.
Plotkin has Zork 1 and Zork 2 up now. Patreon backers can already poke at Zork 3, which goes public May 1. Deadline, the 1982 mystery game where you have 12 hours to solve a murder at the Robner estate, follows on June 1. Starcross is in progress.
The timing makes the project possible. Microsoft, which inherited Infocom through its Activision acquisition, released the original Zork source code under MIT license in November. The code is written in ZIL, a Lisp dialect Infocom built specifically for adventure games. Plotkin's exhibit lets you browse the full source, watch an interactive map fill in as you explore, and step through the logic that turned typed commands into a working dungeon in 1980.
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