You could still disable the inventory
and blank out the graphics for the for the button on the touch screen.
It would still allow for you to get fire flowers and have good level design.
It is just an additional option for making the game harder in a different way.

Its an interesting idea, it would actually take things back more to the gameplay of the original Super Mario Bros.
I would need to do a full playthrough like that to see how it works out though, to make sure there aren't any unintended consequences, and then I might need to rebalance the difficulty of some stages based around that. I will check into it after I finish up world 8.

I was going to do a hack like this once - making small changes to make the game harder.

Like reducing the time limit and replacing goombas with koopas

but I decided to make a hack with new levels

Well I wasn't expecting to finish this quickly, but World 8 is complete!
As for Worlds 4 and 7, I am planning to try to make those exceptionally difficult, since they are secret worlds.

As for the idea of removing the inventory... wont this screw up the toad houses that give you an item? Is there any way I can replace them all with the 1-up houses?

you have a fast process.this seems to be the fastest full hack ever

Well I don't know if I would call it a "full hack", seeing as I haven't even made 1 level from scratch. Its mostly just moving some stuff around and adding some new sprites and objects. Not like that takes much time really... the playtesting takes much more time than the editing.

Well yea.
For making a real hack, from scratch, it can take ages.

I spend DAYS making a single level or tileset.
And even when you think it's finished, you play it again some time later, and then you don't like it, and go back to it and change some things.

Also a really good thing to do about playtesting is ti let a friend play the levels, and look at how he plays them. If he's confused in an area, that's bad. He might also find funny bugs you didn't even think about.

Well, I have finally finished all of the levels!
Worlds 4 and 7 turned out really fun. I would be really interested to know if anyone is able to finish those 2 worlds without using save states, because I know I couldn't :\

In any case, now all that's left is more testing.
I have only tried most of the later levels on an emulator, so I'll be doing a run through on my DS soon.

If you cannot beat your hack without savestates, then there is something seriously wrong with difficulty of your hack and it needs fixing. Difficult is OK, but don't make it too difficult. There is a line between hard and unfair.

How can you beat with savestate but can't without it?
Save is only a tool let you go back to the places.
It will not affect Mario and the level.
If you do nothing wrong, you can absolutely beat it.
_________________________
NSMB6: Beta Testers Wanted!!!

Right, I'm just saying that I personally can't get through those stages without making mistakes, or at least without more lives than the game gives you.
And I intended those 2 worlds to be extremely difficult, but their difficulty does not represent the rest of the game.

Keep in mind that, if YOU can't beat the levels, probably NO ONE does.
Levels are usually easier to you if you've made them because you know them. Other people don't, so that's additional difficulty.

I have added a gameplay video in the first post. This should help to give everyone a better idea of what this hack is like.
I have also put up a new version that fixes a critical bug in an early level, and also fixes some slowdown in a later level.

Alright, I have done lots of playtesting now, and I went back and made modifications to a lot of the levels to even out the difficulty some. Some of the levels should be harder now, while others are a bit easier. I think I'm probably calling this complete now, unless some sort of problems come up.