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.

That's how we used to make GUIs. Miss those days.

Close :) That was http://en.wikipedia.org/wiki/Code_page_437 (or the Unix equivalent I guess). I used the Unicode symbols that roryokane mentioned above, because it has more options for the height of a block (not just half-blocks). You can get Unicode versions of the older drawing symbols from this page http://en.wikipedia.org/wiki/Western_Latin_character_sets_%2...