Small Fix/Improvement

The main reason for this patch is a very strange bug with the reworked sound system which caused corrupted audio after playing for a "random" amount of time usually later though.

It also contains a rework to the pandoras box mechanic making it give 3 cubes and only giving "dangerous" cubes.

AI balance has been slightly improved and some outlier cubes had their AI evaluation adjusted.

The nightmare menu now also shows up in the demo after you "win" a demo run, though you can't select any of them, this is mostly to highlight the fact that higher difficulties exist in the full version.