#1 Don't do anything that doesn't make sense.
Don't do anything that doesn't make sense. Meaning, Don't make someone have to backtrack a far way just in order to a complete the level normally. Don't make someone have to kill themselves because they did a certain part wrong or forgot something. And use the coins to make a safe path through the stage, don't make them lead off cliffs or anywhere unsafe.

#2 Kaizo Stuff
Just.....Nobody needs to see that guys, at all. A. Because Kaizo is nowhere near fun in NSMBWii anyway B. It will always turn out ugly, I guarantee so.

#3 Challenging/Fun > Difficult.
Don't make 1 block jumps, because I don't think anyone has ever found those fun. Adding Enemies at every corner doesn't make a level make a level challenging or fun, just the player trying to figure out how to get over that mess.

#4 Levels can't cause lag.
If a level causes any lag to the game at a certain spot, fix that problem up. A perfect example of this issue is too much 3D models at once.

#5 Timer.
If your level is going to be large, it'll be wise to adjust the time limit to reduce the pressure on people playing the level. For very short levels, 300 seconds works, but for the longer levels, especially ones that use auto-scroll controllers, setting the timer to a larger number is heavily recommended. A good value is the double of what it takes you to complete the level.

#6 Sprite usage.
Learn how to use each sprite properly. Do not use the unused sprites, unless they're capable of working in-game; Ex.: Spinning log is an unused sprite, but it works in-game.

#7 No Sprite spam.
Don't spam your level with Sprites/Enemies. It looks just bad and will also slow down the game.

#8 Areas.
Make sure that different areas make sense. Not something like:
1st area: desert
2nd area: forest
(Note: this can be used depending on how you edit and link the areas, so they will be related)

#9 Use a lot of decoration.
While not possible with all tilesets, try to place a lot of flowers or rocks. If there's no such tiles, you can always place a bush or a sign. This helps the overall look of your level.

#10 Coins.
Don't place coins somewhere impossible to get. Also don't create a path leading to a hole. Coins are usually there, to show the Player one or more right ways to get safely trough the level.


I posted only 10, I would know much more but I want the Community to fill these Rules. So go and post! (Some rules taken from RVLution)
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The spinning log is from NSMB DS... I edited it because it was another NSMBwii enemy before (The log is brown with a green circle in the middle )
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