more passive mobs (turtles, flying birds, moles, squirrels, etc.)
more ambient sounds (hills ->blowing wind, caves -> falling raindrops etc.)
cave overhaul (e.g. very tight creepy tunnels leading somewhere, underwater minilakes with new/glowing mushrooms next to it, stalactites etc.)
more slabs, stairs etc., vertical slabs (like walls)
optimization (less laggy game)
