Okay, time to make a concrete proposal. I have actually changed my mind to some extent after doing some more investigating, and I'm sorry for taking such a belligerent tone with this topic.
I now think that only two trigger areas need changing: the "ghostbuster" trap in the crystal style (which should be moved down 1 pixel), and the rope trap in the pillar style (which should be moved down 2, or maybe 1 -- and maybe also shrunk a bit).
For comparison purposes, the attached level and screenshot show all the traps at the height that would make them only just deadly, under this proposal (i.e. if they were lifted one pixel they would become safe).
Ghostbuster trap: As just mentioned, this affects an official level (Genesis Sunsoft 9). I want to be able to rest the trap snugly on flat terrain, which is especially important as it's long and thin, and burying it one pixel in terrain loses a lot of visibility. The middle portion would then have 2 pixels showing above ground, which is consistent with other traps (see screenshot and further discussion below).
I would prefer to move the trigger area rather than expand it, as it's already 6 pixels tall, and with the trap being so thin, it looks wrong that lemmings can still be killed when moving high over the visible part of the trap.
(No other trap triggers from the official styles are more than 6 pixels in either dimension. In fact, this is the only trap with a trigger area wider than 4, so maybe it should also be shrunk horizontally? If you look closely then it looks a bit weird, because the lemming is suddenly displaced to the centre for the death animation -- but most of the time this isn't something you would notice.)
Rope trap: This also affects an official level (Fun 15 / Taxing 1). On that level, the bottom metal bar is in fact buried 1 pixel, so moving the trigger area down 1 would be enough to make it deadly. However, I'd like to be able to keep the metal bar unburied (which would require moving the trigger area down 2) as this looks better, at least as regards the support structure. However, there is a counter-argument: if you look closely, you can see a ring of darker pixels on the top 4 rows of the dirt mound. This represents the rope that the lemmings have to step on to trigger the trap. If the metal bar is unburied, then the rope is entirely
above ground (there is one pixel in between the top of the terrain and the bottom of the rope). So maybe it should be safe at that height (i.e. move the trigger area only down 1?)
For this one, I feel strongly that the trigger area (currently 6 pixels tall) should be moved and not expanded, and maybe even shrunk. As I just said, what kills the lemmings is stepping on the loop of rope -- it should be entirely safe to pass above it.
* * *
For the other traps, I'll explain why I now believe it's best to leave them as they are. I originally proposed that the marble squasher and 10-ton weight also needed adjustment. I've taken a look through the original levels, and noticed that on levels using these traps (e.g.
Fun 24 and
Taxing 2), the "pressure plate" (the part that the lemming steps on) is partly or completely buried, so these traps shouldn't be causing any problems with original levels. Also, the plate for the marble squasher trap is 3 pixels tall; that for the 10-ton weight is 4 tall. That's enough that if the entire plate is above ground, it looks as if the lemmings are walking past it and it
should be safe. So I now think that I made the wrong call here originally -- though since Simon and others supported my original proposal, I wonder what they think about these traps in particular.
So I now suggest that these traps should be left as they are, which means that if the top 2 pixels of the plate are above ground, the lemming will step on it. As I said earlier, that's consistent with the height of the middle part of the "ghostbuster" trap (and also the bottom platform of the wheel).
