Well, this blew my mind: macintosh.js.
This is Mac OS 8, running in an Electron app pretending to be a 1991 Macintosh Quadra. Yes, it’s the full thing. I’m sorry.
My second Mac was a Quadra 950, purchased in 1991. Twenty-nine years later, here’s an emulator of that beast of a machine running on my MacBook Pro.