I've been making my own hack for a few weeks. I found that it's not easy to make a fun level. I want it to be interesting and difficult at the same time. But it really takes a lot of brains. It may take me about a day to make a level. At least one afternoon,Think about the route of each level, the platform, and the position of stars and coins,The length of each level is also a little difficult for me to decide.I did four levels in a week，I want to ask you how to control the length and difficulty of each level. I also want to know how long it takes you to do each level.

I've also played some hacks, such as skylander's smbu for DS and newer version of newer team. I feel that everyone's creativity is different ha ha ha! Those levels are great, even Nintendo's official feeling

If you can, I hope to provide some suggestions
（My English is not very good, so I use the translation software. Please forgive me for my mistakes）

So, here's some general advice. I'll give examples of hacks that do (or don't) follow each points as reference, since looking at other levels is a big part of the learning process:

• You need a gimmick, something that sets your level apart from other levels. Try to focus your level on that gimmick. Use it in increasingly complex and creative ways throughout the stage. I typically pick a random object that fits with the theme and try coming up with as many ways as possible to use it. Public code hacks can also heavily increase the possibilities, especially ones like the actor spawner and rotation controller which can be used with anything. Newer DS does this extremely well. The original NSMBDS not so much.
  
• Balancing difficulty is hard. Sorry, but I don't have much in the way of advice here. Even modern triple A games struggle with difficulty curves. It's something you always have to spend a lot of time thinking about and adjusting. Newer DS does this decently well, but even it has some difficulty spikes. Make sure to ask for the thoughts of demo players and beta testers, as there are things that are bound be more difficult or less obvious for players than they to the creator.
  
• Everything must be hinted at in some way. You can use rows of coins or clever tiling, but all secrets and elements necessary for progression (besides things like Easter eggs which don't matter for 100% completion) must be possible to find without a guide. Unmarked invisible vine blocks leading to a star coin or secret exit are bad. "Kaizo" invisible block traps are even worse.
  
• Level length is pretty easy. Look at the length of original NSMB levels and try to replicate that. Since many of them are considered to be a bit on the shorter side, there's no harm in doing levels that are slightly longer. Newer DS has basically perfect level length. Sometimes, I create the view before the level and design the level trying to fill the view. If you're having a hard time getting the sizes you want, that can be a good idea. Just make sure your checkpoint is indeed somewhere in the middle to avoid making the player go through long stretches of level without checkpoints, as that can be quite frustrating when you die.
  
• Be creative. If you think of something nice that hasn't been done before, then go for it. Unique levels can be a lot of fun.

Here's also some more subjective advice. This stuff is things that bother me when I see them, but that I rarely see mentioned by others, so I'm probably the only one who cares:

• Make sure your tiling is good. Try not to have any seams. Even big hacks like Newer DS have quite a few (subtle) seams and it bothers me like crazy. I always thought it looked cheap, so I make sure to always avoid them, even at the cost of bloating my tilesets with barely used tiles.
  
• Don't hide a star coin in the same place as a secret exit. Once again something Newer DS and many other hacks do and it's always felt lazy to me. Also, make sure everything is actually locked behind some sort of challenge. Star coins that are just out in the open are super lame and NSMBDS is guilty of having a few of those.
  
• This also a graphic design thing, but it also has to be incorporated into level design. Make things look natural. Big flat spaces? Avoid. Lack of decoration? Avoid. Random platforms of jyotyu wooden blocks and the like don't usually look good. Try to find something in your tileset that can be used instead and fit the level's theme. If you can't find anything like that, then add it to the tileset. This is something Newer DS excels at. Minor seams aside, the levels are all very natural-looking and visually interesting.
  
• Put blue shells in water levels. Please.

I spent way too long writing this, so I hope it has been useful.
_________________________
Nothing to say, so jadnjkfmnjamnfjkldnajfnjkanfjdksan jsdnvj m.

I feel inspired. Thank you. It's very useful to me!

Good level design is harder than you'd think. That's probably why a lot of Mario Maker 1+2 levels suck.

One level takes me around two weeks hajaha

two weeks for one level。。A good level takes a lot of time，@seteven i really want to play your level haha。i will Go to your homepage later

mario maker levels suck I think it is because it is not as comprehensive as the parts of nsmbe, which will make the level look less beautiful. And anyone can do the level@KingYoshi

your level looks so difficult haha

Maybe it is, to me a level takes me 5 hours in a day, maybe he blocks too much, it happens to all of us, once I blocked for 2 days and just now I blocked too, the levels of puzzles tend to be more difficult than the normal ones and can there was more bloking in you head
_________________________
The star project that shows my brilliant mind

I'll keep that in mind. Thnx,  poudink!
_________________________
Do U like this footer???
Well, neither do I.