Yeah. I notice that too: not symmetric ladder. Why? Take a look at Gens! it's very strange...
I think the upper left is mixing shadow with normal then highlight with normal using pixel special codes to get a 16 (not 17) color gradient. However, it seems it does not work on real hardware as expected and highlight mode is not set for colors 0-7. Sourcecode would be useful here
Also note that the maximal palette is quite limited:
- colors 0,1,2,3 in normal mode are the same as colors 0,2,4,6 in shadow mode.
- colors 4,5,6,7 in normal mode are the same as colors 1,3,5,7 in highlight mode.
- color 7 in shadow mode is the same as color 0 in highlight mode.
The weirdest thing is still color levels are not linear but rather "compressed" in the middle. Very surprising.
What game use H32 mode? Or give me demo, wich do that.
You will also need a game or demo that uses Horizontal Interrupt, I will try to find one or make myself (the trickiest part I faced is how to display text in my ROM, can't find any good example of font embedding/displaying with sourcecode)