Thanks, everyone! I have taken a look at the 2 player levels from the Extra Levels pack, and it seems like the original Amiga 2 player levels are interspersed with some custom made ones (?). For example, in the original version, "Still everything worth to play for" is the second level already; in Extra Levels, it is the third - the second one being a level called "We're in this one together". Notably, those custom made 2 player levels seem a lot harder than the original ones
. The original Amiga levels often barely required a particular player to do anything, but seemed more like a "battlefield", i.e. enough space between trap door and exit to steal each others lemmings and lure them into one's own exit.
While We're on the subject of 2P levels, I had an Idea
The 2P levels but designed for one player
This post has kind of inspired me to make something out of a few of the 2 player levels.
Ah, I see there's much ambition for this around here!
Well, at first glance that already seems to be the case in the 2 P rank of Extra Levels, as I have found out now - there's only one player, Lemmings are coming out both ways, so theoretically they already are "2 player levels for one player".
However, the major problem is the "indifference" of the exits. The original purpose of many of those levels was having the blue lemmings' trap door right next to the green lemmings' exit and vice versa, so you would have to get around your opponent's exit as if it were a trap, in order not to give them any benefits.
With just a single player however, it doesn't matter which exit lemmings enter, so many of these levels just solve themselves . I imagine this would be a perfect place to use "limited number exits" that only allow a certain number of lemmings in before they "close" like a locked exit (at least that's the way this works in Pit Droids; effectively, I guess it's just that the exit trigger disappears). But even that would only solve part of the issue, because if both players have e.g. 40 Lemmings and both exits can hold up to 40 lemmings, a single player could still have the lemmings from each trap door just walk straight to the exit nearby rather than solving the actual level.
So what would be required for this? The other kind of "limited exits" that only allow climbers / floaters etc. in? That's another Pit Droids feature, by the way, where there were exits that only allowed droids with certain colours or tools to enter, so I'd support that idea in general.
Or we would actually have to have two different lemming sprites in these levels, like in the original version, but make it so that only blue pants Lemmings can enter the exit with the blue flag, and the same for the green ones and the green exit.
I'm just trying to remember, wasn't this the way the balloon exits in Lemmings Revolution worked? Meaning water lemmings could only enter the white balloon with the blue-haired head on it, and regular lemmings could only enter the blue, green-haired balloon? I certainly remember there were red balloons that allowed all three kinds of lemmings (regular, water, and acid) to enter; that's why I conclude the mono-coloured balloons were lemming sprite-specific.