It's not really about producing charts, it's about putting charts where you normally couldn't. World primary energy use by %: Oil 34.77, Coal 29.36, NG 23.76, Nuke 5.47, Hydro 6.63 █▇▅▁▂
There isn't anywhere this lets me put a chart that I can't today. Computers are capable of rendering non-font content, even if it sometimes seems otherwise.
how did you do that?
The black rectangles are just Unicode characters – for example, “▅” is character U+2585 LOWER FIVE EIGHTHS BLOCK. sp332 probably either used https://github.com/holman/spark or manually copied and pasted those characters.