Sprite priority handling
If presented with multiple sprite lumps that cover the same frame, Dday appears to prioritize them differently to Chocolate Doom.
Dday appears to prioritize in the order of 1,2,3. But Chocolate Doom appears to prioritize in the order of 3,2,1. This actually means Dday can end up using both A0 and A2A8/A2+A8 at the same time.
I admit that I haven't tested this one against Vanilla Doom, but I have read that Vanilla Doom should match Chocolate Doom in this regard (and it would be a mistake in Chocolate Doom if it didn't match Vanilla with this).
#3 Updated by danij about 5 years ago
Evidently this is also sensitive to the load order. In the above example, if one provides an additional POSSA0 lump after the supplementary sprites for the other rotations - vanilla will ignore the extra rotations and use POSSA0 for all.
Clearly a vanilla-compatible mechanism will require special case handling for this quirky behavior.