Just the 3rd or 4th hatchery. It's too damn difficult :< Between the giant worm and the beetles and the hounds and the difficult controls/mechanics I just can't do it. Still trying though..
I came close to finishing the 4th hatchery but I forgot to press up at the door, flew right through it, and landed on a beetle. Did the same thing later but landed on the worm. Perhaps simply touching the door could bring you to the next level?
I really want to say you should lighten up the difficulty a bit (atleast for the Hatchery, that's a hell of a difficulty curve) but it's your game so :) I just fear whatever comes after the hatchery will be entirely impassable, especially to more modern/casual gamers.