Glad you enjoyed it! I hope the difficulty isn't as over-the-place as for Lemmings World Tour, since a) Lemmings Open Air underwent pre-release testing, Lemmings World Tour did not, and b) the levels were a little freer to move around the ranks, compared to the World-Tour levels, which were more thematically tied to the rank names.

I like the tileset on "Golden Hills"! Reminds me of my own Autumn tileset, but with a much higher resolution.

The reason oh-noing is expected is because the lemming’s position marker is inside the wall, i.e. on terrain.
This is different from Swimmers and Shimmiers, for example, who have no terrain under / at their position marker.

Arriving at the top makes more sense, and is mechanically more consisent, since all non-ranged destructive skills (Basher, Miner, Digger, Fencer) arrive at the end of their respective tunnels, too.

Thinking about it, Swimmers being able to jump out of water should really have been a feature in the Lemmings clone for Linux, named "Pingus" ...
Because while we were wondering about how this is physically possible, penguins can definitely do that!

To clarify: Not L3 (Lemmings 3: An All New World of Lemmings), but Lemmings 3D.
The Turner was just the 3D-version of the Blocker, turning lemmings around left or right corners — rather than upward, which is what the transitioning state we’re currently talking about would be doing.

This distinction however has just made me think of what the Shimmier would look like if it were implemented in Lemmings 3D / Loap…

I'm making progress in fixing the first batch of backroutes for the Gold and Platinum rank - only a few more Platinum levels left to go before I can send another version to kaywhyn.

So far, the levels didn't turn out as backroute-prone as I feared - and for the few glaring ones I left open, the fixes were usually the easiest (just some extra steel / one-way arrows). For one particular level, a trap did the trick by blocking off a route. Since this was a Shadow level, I didn't want to use one of the standard L2 Shadow stompers here (the ones with the red exclamation marks), since the top part always looks like a walkable steel square. Normally, these traps go on top of terrain - having one just by itself, without actual steel under the red exclamation mark, would be confusing. Hence, I went with the red-eyes trap from L2 Cavelem instead, which does seem to go along with the L2 Shadow tileset quite nicely.

Neat! I somehow remember the "R" icon that grows and shrinks, but I don't know from where. Was that a SuperLemmix feature? Or from SuperLemmini?

Also, I see you were having fun toying around with the new skills on "The Grand Puzzle" from Lemmings World Tour... (I assume you took the level file from the unofficial conversion by jkapp, since there is no official release for SuperLemmix yet...)