Here's a somewhat artistic level I just made in the Machine style, called The "What The Lemming" Machine.
40 lemmings, save 35, release rate 1, no time limit.
10 Climbers, 10 Floaters, 1 Glider, 5 Builders, 2 Bashers.
I've currently got it placed in early-Edgy, but that may be subject to change.