I'm Arceus88, I discovered SMBX since I was searching for a level editor in Mario, then I found this, but I don't remember where I'd download SMBX, not from here. My first original level was an invasion level but still I don't know how to use SMBX. I've already figured it out how to do this, because the Invasion episode gave me clue to edit custom graphics. Then I've created an upcoming episode, Bowser's Adventure. Well, I think I have to cancel this, do not ask why. I'll keep being active in this forum. And also, don't forget to download the demo version of Bowser's Adventure!
Please try my project (I'm begging you. ). The full version will be released in Middle or Late 2016.
Note: The boss rush will be available in the release, so it's not yet available.