Lock and Key [Difficulty: Hard]

[92Dexter11]

This time, this should be intended  (plus a similar but backroute-ish alternative solution )

Both solutions are valid!

[namida]

I didn't play through it, but looking at the description and screenshots: I'd actually say "every level revolves around a locked exit" is the more "gimmicky" thing here than the one lemming. However, I'll also stress that in this case, I don't mean "gimmicky" in a bad way - it's a perfectly valid, fair and (in and of itself) non-frustrating style of level design, the only thing "unusual" is it showing up in every level of the pack.