Infinite Mac
Just spent my lunch break playing around with Infinite Mac, a collection of System Software/Mac OS and NeXTStep/OPENSTEP from the 80s/90s, emulated in-browser.
Coming from 16-bit Windows, and Linux kernel 2.0-era distros, my first MacOS was Tiger, shortly after Apple transitioned from PPC to x86. I was only slightly familiar with System 7 as my high school friend at the time had a Quadra (fun site note: he was the first person to tell me about this new thing called the "world wide web", accessible with something called "Mosaic").
Anyways, I started with System 1 and moved from there. Pretty cool seeing how far the operating system has evolved. Some OG games in there too. Launching Netscape brought a nostalgic tear to my eye. Just reminded me of the experience of web 1.0 and just exploring random sites. Sadly networking didn't work. Maybe I'm missing an RTFM somewhere.