I just came across this interesting bit of computing history.
Back in 1982, there was a peripheral that turned an Atari 2600 into an (incredibly simple, ZX-81 level) home computer, including a keyboard, BASIC, and cadette support.
But the addon is/was incredibly rare, and there's very little information about it online.
So it's interesting to see there's now a video up on YouTube profiling this device (known as a Spectravideo CompuMate) and how it works...