So I got bored today and started looking at the pgm2yks.c

Here's a few lines from the file

0x000000, 0x00007c, 0x0000f8, 0x000174, 0x0001f0, 0x00026c, 0x0002e8, 0x000364,

0x0003e0, 0x00045c, 0x0004d8, 0x000554, 0x0005d0, 0x00064c, 0x0006c8, 0x000744,

0x0007c0, 0x00083c, 0x0008b8, 0x000934, 0x0009b0, 0x000a2c, 0x000aa8, 0x000b24,

0x000ba0, 0x000c1c, 0x000c98, 0x000d14, 0x000d90, 0x000e0c, 0x000e88, 0x000f04,

0x000f80, 0x000ffc, 0x001078, 0x0010f4, 0x001170, 0x0011ec, 0x001268, 0x0012e4,

Here's what I got with the algo below

0x000000, 0x00007c, 0x0000f8, 0x000174, 0x0001f0, 0x00026c, 0x0002e8, 0x000364,

0x0003e0, 0x00045c, 0x0004d8, 0x000554, 0x0005d0, 0x00064c, 0x0006c8, 0x000744,

0x0007c0, 0x00083c, 0x0008b8, 0x000934, 0x0009b0, 0x000a2c, 0x000aa8, 0x000b24,

0x000ba0, 0x000c1c, 0x000c98, 0x000d14, 0x000d90, 0x000e0c, 0x000e88, 0x000f04,

0x000f80, 0x0010fc, 0x001078, 0x0011f4, 0x001170, 0x0012ec, 0x001268, 0x0013e4,

It's not 100 percent, and it gets worse as you go through the file (0x3c00 values),

but there are some bits of the decrypted addresses that are correct throughout

pretty much the whole file, so I'm fairly certain that I'm on the right path.

unsigned int nret(unsigned int sprite_no)
{
unsigned int i, a  = 0x007c;

for (i = 0; i < 32; i++)
{
	if (sprite_no & (1 << i))
	{
		a ^= 0x84 << i;
	}
}

return a;
}