A very powerful super mario bros 3 editor by the DarkDaiz, the creator of Mario Adventure. It is still in beta

This new editor is different from the others because it completely rewrites the level data format. Instead of object-based level data where you are restricted to using objects comprising of specific 16x16 tiles, the level is instead made up of these 16x16 tiles and nothing else. Tile placement works much like it does in Lunar Magic's direct Map16 tiles.

There are still some bugs being debugged before it's publicly released