I'm having a problem with my palette for my first demo. After reading the post of Pulper's thx demo I've been able to fix all the problems in my demo except for the palette.

I use 3 main emulators to test my code. Theres Nestopia, Nintendulator, and VirtuaNes.

The whole demo works perfectly on Nestopia (although it doesn't give me any debug options to check the palette or nothing), it doesn't give the right colors in VirtuaNes (I looked a palette viewer and pretty much all the entries in it are grey with a few exceptions like green and purple) and all the sprites are grey (the same grey because grey is basically the whole palette) but the main primary color is black (except when you die, the background primary color changes to a random color). And in Nintendulator the colors are even more different.....the background is light blue and the sprites are green and grey.

So basically the palette is different in each emulator and only Nestopia has the correct palette (the one I expect it to have). I assume I'm not doing something before initializing the palette that for some reason Nestopia isn't picking up. I'm gonna try some more tests to see if I can get it to work. thx :)

Well, after some testing I figured it out. I was writing the palette ($3F00) after I already set up the PPU (instead of before). So nestopia and fce ultra accepted the writes to $3F00 after I set up the PPU, while Nintendulator and VirtuaNes didn't. So I got a few questions now.

1. How would a real NES work (would it allow the writes after setting up the PPU, or would it not?)?

2. I know that it is possible to change the palette values after setting up the PPU, but my question is how? What was I doing wrong? And why did my writes to $3F00 not work after setting up the PPU? thx :)

The PPU is using the address pointer internally when drawing the picture, that's the same pointer as you are using when you write to the palette memory.

You should disable the PPU when you want to access memory through it, if it isn't for a small amount of time. Then it could be enough during the vertical blanking period.
But you have to disable it if you want to do it in the middle of the screen.

Ohhh, thx that makes perfect sense. Man I'm stupid. Lol suprised I made my first demo heh. thx :-)