Noticed something weird in level COVOX Lemmings - Taxing - IceTown: lemmings do fall into the frozen water instead of being drown!
...these objects were deliberately marked as fake to imitate the original game.)
Is there a way to implement a switch to become fully compatible with Lemmini? I like its engine, but I prefer SuperLemmini due to its GUI improvements.
Technically, yes, it's possible, but it would be more trouble than I think it's worth. There are just so many little differences between Lemmini and SuperLemmini that implementing such a feature would mean that pretty much every part of the lemming logic code would require two paths (one for Lemmini and another for SuperLemmini), making the code considerably more complex and harder to maintain. On top of that, almost every lemming and object mask would need two versions, since those are different as well.
Despite being based on Lemmini and being able to load Lemmini levels, SuperLemmini is meant to be more like "original Lemmings with improvements" rather than "Lemmini with improvements". With that said, I do try to be somewhat compatible with Lemmini as a secondary objective, but there are practical limits to how far I can go with that.
Another one, in level Lemmings Companion - Fun - For Every Lemming, Turn, Turn... the trap on the left does not trigger. Is this due to different game mechanics or wrong positioning?
In this case, the trap actually does work, but it's placed a little too high. If you build where the trigger area is (on the left), the trap should start killing lemmings.
So, this is another difference compared to Lemmini. There it works just fine.
I had forgotten to say that the trap doesn't work right in the original DOS version either for the same reason. So this is another case of an oversight on the part of the level author.
Could you attach the problematic level file so that I can maybe determine what went wrong?
You're lucky I still have some of the old levels I did for testing SuperLemmini 0.103b. Here's one of them, it should have the same problem.
Whatever version of NeoLemmix you used was writing terrain entries incorrectly. Here is an example of such an entry from your level:
terrain_0 = 25, 1521, -114, 0, 0, 1
The first four values there (the ones in bold) are the only ones that should have been written; the other two never had any meaning until SuperLemmini 0.104, which uses the fifth value (if it exists) to indicate which style the terrain piece should come from. The value there is "0", so SuperLemmini tries to load that terrain piece from a style called "0" (which, of course, doesn't exist). (And if you're wondering, if you load the level in Lemmini, the terrain doesn't show up at all, because Lemmini expects terrain entries to have
exactly four values, whereas SuperLemmini expects
at least four values.)