It's kind of like discovering the assembly monitor on the Apple ][, which you could get to by poking a value in Basic. I remember typing in an assembly program I found in a magazine that sampled audio from the cassette recorder, and played it back on the speaker. It was gritty sounding, but an amazing discovery for me at the time (about 1982).
(I'm always doing Ctrl-Shift-C to copy text from the browser when I forget I'm not in the terminal anymore--which brings up the element inspector and the console. I've always wanted to explore it myself, but I'm usually deep into another project.)
I wonder what I could have done if I had Three.js?
https://en.wikipedia.org/wiki/IBM_BASIC#IBM_Cassette_BASIC
no OS needed, like the Apple ][, TRS-80, etc.
IIRC, nothing in either volume of the original (not sure if this changed in the later update that targeted SmallBasic) used graphics, they were all text-mode, so there's no real need to target a canvas library. Maybe something that provides a simpler abstraction than the DOM for just dropping text onto the page, though, if you don't want all the display in dev tools.