Xor World

Obscure but interesting puzzle-game that never
saw a release. (The title screen says "1990",
so that's where the year comes from.)

The music is some nice Blues stuff, though it
is way too simple for the SAA sound chip.
(It uses only 3 out of 6 channels.)


This is the game I used to test the SAA1099
code of VGMPlay and the VGM tools.


Although the game has a sound test, it doesn't
seem to work. So I hacked the game to play
the required songs.
In order to play a song or SFX, you need to
set FFCFE0 to FF (or anything else that is not
zero) and put the actual Sound ID into FFCFE1.

ID ranges:
    00-7F - dummy
    80-EF - sequences (songs+sfx)
    F0-FF - special commands

The Sound ID is processed at 00BAF6.
The Sound Queue (FFCFEC-FFD00B) is processed at
000E60.

SFX/Music ID List: 00080E
(00-7F = SFX, 80-FF = Music)

Sound IDs 9D-A1 are not in the list, so they
are probably unused. Playing Sound ID 85 makes
the sound driver alternate between ID 85 
(Main BGM 1) and A2 (Main BGM 2).


Size reduction (vgm_cmp):
    905 KB -> 356 KB (39.3 %)

— Valley Bell

Source: VGMRips