It looks okay to me. Remember that 40 lemmings come out of each trapdoor, and it's easy to forget about the ones on top if you build over the digger trench.
I quite like Bat Country too, especially the detail in the scenery. The start is a little bit tricky, although once you get out of Picnic, the levels reach a Mayhem level of difficulty quite quickly (indeed, I designed Crystal Caves to be a "classic Mayhem" level with the slightly awkward design, limited tools, and giving the player 20 bombers when you need to rescue 100%!)