Altair 8800 Simulator
s2js.com
s2js.com
https://www.autometer.de/unix4fun/z80pack/screenshots/2014.h...
Comes with prepackaged CP/M images and can run Alan Cox's amazing FUZIX system:
https://github.com/EtchedPixels/FUZIX
https://hackaday.com/2017/04/16/z80-fuzix-is-like-old-fashio...
I assure you the Altairs were quite useful. Mostly, owners enjoyed the luxury of working on their very own computer, rather than a time-share machine's account from the corporation or university.
It's difficult to communicate how this felt, in this age of ubiquitous computing. A machine that one could reboot whenever you wanted. Tinker. Explore. They wrote games. Controlled hardware. Learned what made a computer tick. Connect a modem and talk to others. Sure, it was primitive, but at the time it felt as cutting-edge as space travel.
If I recall correctly, the Altair ran CP/M, and could run the early Zork infocom text adventure series.
I did some research after posting that and realized that you could get teletype terminals for them. This makes it much easier to see what people did. I originally thought that most people punched op-codes into that front panel, which seems like an awful lot of work for not much reward.