Tip: You can use Lunar Magic's Overworld Layer 3 Editing system to edit or create your own layer 3 images (castle bricks, fish, rocks) and apply unique effects per level via the Layer 3 Bypass in the main editor.
i dont see how to activate the secret exit (??) of the 1st level (misterious place) unless with some real cheese or maybe some tas help. Even if you can get up there by goomba jumping, the screen doesnt scroll and you basically cant see where you are going. But maybe im missing something else..
Edit: im really dumb.. its way easier than i previously thought