World 2-3 (Super Mario Maker for Nintendo 3DS)
From the Super Mario Wiki, the Mario encyclopedia
Because of the mechanics of Super Mario Maker, it is just long up and down tracks with a lift going down on each one. Also, short versions of each world replace their respected worlds. In each one, the player must find a key and open the locked door. However, it appears that in world 4, it is possible to leave it, but not without getting the key because it is in a Lakitu. The other keys are out in the open and in a Question Mark Block in 3 and 2 respectively. The only enemies not in the original 1-2 are the aforementioned Lakitu and two Koopa Paratroopas.