Why is there graphics glitching when you change $2005 or $2006 mid-screen?
The general reason is that the NES’ PPU operates on the level of characters, not individual pixels. The PPU only cares about what character it’s displaying, not what pixel it’s at. So, when you do things like change the scrolling or change the address from which $2006 should be reading, it’ll sometimes mess up the finer details like pixel-perfect scrolling and such. Blah. Ya just gotta live with it. • Is the NES palette RGB or what? No. I wish it was, but it isn’t. The NES really works on the NTSC colour concept, with luminance [brightness] going in one direction, and chrominance [hue] going in another. Barring the colour values after $xC, the palette in the NES does on average a 30 rotation in hue for each step of the lower nybble that you take. Furthermore, the palette increases in luminance for each step of the upper nybble that you take. So, the palette really operates on hue and brightness in each direction, not RGB in each direction. • How do I get an accurate palette then? Well,
