New core added for RetroArch Steam brought to you by icculus
https://store.steampowered.com/app/2246910/RetroArch__MojoZork/
You can download this core either from within RetroArch Steam by going to Manage Cores, or by simply downloading it for free from Steam.
There are now 55 cores available in total for RetroArch Steam.
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https://www.youtube.com/watch?v=Ps9uB8tY1HI
This is an implementation of Infocom's Z-Machine. The Z-Machine is a virtual machine that's something like a high-level CPU. To keep their games portable and easier to write, Infocom's games all use this fake processor and ship with a platform-specific Z-Machine "emulator" ... so a game could run wherever someone had implemented the Z-Machine.
This project is just for fun; everyone should write this at some point as an educational activity. If you want a serious Z-Machine implementation, there are certainly better ones out there (I personally recommend "Frotz" and there are many others, too).
This program currently supports most of the Version 3 Z-Machine. This is enough to play the vast majority of Infocom's catalog. Later Infocom games used version 4, 5, and 6 of the Z-Machine, and those will currently not run here. Most modern Interactive Fiction is built with a tool called Inform and usually targets version 5 at the lowest; these games currently don't work with this project. Maybe later.
If you want to write your own Z-Machine, there is an "official" specification on how to implement it, written by people that spent significant time reverse engineering the originals from Infocom, and extending the ecosystem with new tools. You can find that specification here.
As usual, Wikipedia offers a wonderful rabbit hole to fall down, too, in their Z-machine article.