If you're curious about emulating even older apple devices (Clickwheel iPod), I worked on an emulator for a few months called `clicky`. Very nifty project, given the weird and undocumented architecture of those early iPods
Any chance I could borrow this code for my (very WIP) classic clickwheel iPod emulator? I've actually got an experimental WASM build of it up and running, so this would be super appropriate!
One of the coolest technical aspects of early Infocom text adventure games is that most games weren't actually written using native assembly code for the platforms they ran on, and were instead compiled down to "z-code", a bytecode which ran on the "z-machine" virtual machine architecture. Z-machines are pretty niftly little bits of tech, as while they have a lot in common with regular 'ol machine code, the z-machine spec also includes dedicated instructions for fetching text input from the user, outputting text to the console, saving/loading data to disk, etc...
Having games target the abstract z-machine platform made it incredibly easy for Infocom to port games across platforms, as instead of re-writing every game from scratch, they could simply write a z-machine interpreter for said platform, and immediately gain access to their entire adventure game catalog!
A happy side-effect of all this is that it's super easy to run these classic adventure games on modern platforms, as instead of emulating the UI/UX of a 80s microcomputer, it's possible to write a z-machine interpreter that takes full advantage of modern GUIs.
One of my personal favorite modern z-machine interpreters is `encrusted` [1], which is written in Rust that runs on the Web thanks to WebAssembly. As a fun side-project, I ended up forking the project and making `embcrusted` [2], a z-machine interpreter that can run on embedded platforms without a full C-library. In a weekend or two of hacking, I was able to port a z-machine interpreter to my mechanical keyboard, in order to get the "authentic" experience of playing a text-adventure game through a teletype :)
[clicky](https://github.com/daniel5151/clicky) is an emulator for Clickwheel iPods I worked on in the many boring months between University graduation and starting full time work.
Unlike retro consoles/handhelds, there doesn't seem to be much nostalgia in the public consciousness for OG iPods - which is fair, given that most people just see them as antiquated MP3 players. That said, some of the later models did have some pretty neat little games which have yet to be preserved, and can only be played by owning the original hardware.
It was a lot of fun hacking away at the project, and I'd made a surprising amount of progress given that I'd opted to roll my own full-system emulator (in Rust!) as opposed to using something like QEMU.
Who knows, maybe when I have more free time I'll revisit the project and keep pushing it closer to completion. Not sure when though - emulation is a real time hog when you're also juggling a full time job!
I actually had to wrestle with this exact effect while working on wideNES [1]. By saving a screenshot of the screen at each frame alongside with it's PPUSCROLL value, it's possible to gradually build-up a map of the level as it's explored. Moreover, on subsequent playthroughs of the same level, it's possible to sync the map with the on-screen action, effectively enabling a "widescreen" mode for old NES games (with certain limitations).
Lots of games used funky scrolling mechanics, typically to create status bars, but of all the different games I tested with, TLOZ was by-far the weirdest, requiring an entire special case to get working!
I don't have any screenshots of my own, but some japanese website recently covered wideNES, posting screenshots of it working with the original Legent of Zelda.[2]
The Nesdev wiki is the bible for writing NES emulators. It has all the technical documentation you'll need to implement the various aspects of NES hardware. It also has plenty of test ROMs, which are incredibly useful for verifying implementation details!
Fair warning, while it's pretty easy to get a half-decent 6502 emulator up and running, implementing the PPU is incredibly tricky. If you don't have a lot of experience writing emulators, I'd recommend starting with a simpler system, like the CHIP-8, before tackling the NES.
https://github.com/daniel5151/clicky