Without being pedantic, a Genesis/Mega Drive emulator and Lemmings ROM. =P
And some of them are pretty hard yeah, but you might not find them quite so hard yourself. Certainly the Present and Sunsoft difficulties range from being stupidly easy to stupidly hard, you need to think outside the box for some of them. Like on one level you need to get one, and only one, Lemming out of a line of Lemmings coming at a RR of 99, but you don't have any climbers or blockers to block the rest in. But then at the other end there's one level called "Everyone turn left" where you have only one blocker skill and an uninterrupted stretch of land, so it doesn't take a genius to work out how to do that one.
