Love it!
It is unfortunate that the scenery is positioned in such a way that lemmings end up falling by the side all the way to the bottom of the screen.
Perhaps it would look better if you removed the padding from <body> and added more pits to the scenery.
Right, I thought the same. Construct it such that a Lemming falling down from the top will have to clear every level to the bottom instead of just falling past all of them.