How so?
All "graphics" are made combining ascii characters, even the backgrounds.
Here's the font source https://style64.org/c64-truetype?fbclid=IwAR2oi_TPw8ouLK9FPeAzHnrNfzHa8MKyiq6YoJ...
And they're not prerendered as pngs, they are just plainly in the code and then rendered
Here's the source code https://github.com/Oscetch/jam.ascii