Xenon 2 - black screen when starting the game

[ITotalJustice]

The game reaches the title screen, however starting the game causes a black screen, although the audio continues to play.

Interestingly, disabling audio in the menu then allows the game to continue to work. I am quite sure this is interrupt related.

May also be related to #27

[ITotalJustice]

i don't think this is related to register R. the game only uses this for the background stars. basically, using it a rng number.

you can disable this effect by setting REG_A=0 in LD_A_R)

[ITotalJustice]

the game can also play the demo just fine (happens if you idle too long on the title screen) with audio. kinda baffled by this...