SP4CEBAR 2023-01-25 09:38 (Edited)
I'm a little late to this but, it uses 40 characters (in registers), it's based on the fact that:
20 characters * 16 bytes = 8 rasters * 40 bytes
It's a bummer that it uses 35% CPU passively
I guess I could reduce that if I make it copy 20 bytes per raster instead of 40 bytes and use 160 characters (in registers) to prepare one half of the screen and refresh the second half
The address ROM generator I use for the line drawing and the other shapes should split its generated addresses to say that one-half of the pixels go to the characters and the other half go to RAM to be loaded via the raster FX
