LogFAQs > #974585474

I've sort of finished it twice, between finishing all the levels individually in For Super Players mode in SMB DX back when it came out, and worlds 1-9 in All Stars recently after it was added to the NSO app.

I don't think it's all that difficult for the most part (maybe about 5 or 6 levels in the first 8 worlds are fairly tough. haven't really put in the effort to try to beat worlds A to D), if you're playing a version that gives you infinite tries. It's much more difficult if you're playing the original version, where you get kicked back to the beginning of the world if you continue, and can only really stock up on extra lives in the first stage and they have to last you the entire game.