First of all I have to say that I know the author of this file, so take this review as you will.
To understand how to beat this world you must know a little bit about Super Mario 86 v0.91. It is a great program, however there are many glitches in the program, nothing that will mess up your calculator, but just some stuff that makes the gameplay different from other Mario games of the past. For example, in certain circumstances you can actually walk through walls (For a list of all the glitches found thus far see the file titled "Glitches Exposed" in the same directory as this file. It has all the glitches that have been found for the program as well as a walk through documentation on how they work).
Anyway, back to the file at hand. I will protest that this is the hardest world ever created for Super Mario 86 v0.91. It has 40 levels as stated and they vary from Bowser-infested levels to complete brain thinkers. You will come across many levels that "look" physically impossible. However, I can assure you they are. This is because the world requires that you know how the glitches work, thus why I mentioned the above file and why you should take a look at it.
I have beaten every single world made for this version of Mario with the exception of this one. It will always be on my calculator until I beat it. I take certain pride in this world partly because I know how it evolved to be how it is today, but I can assure you that if you are a Mario fan of any kind this program will test you to your fullest. I highly recommend this file simply because it is different, (well with the exception of my worlds :-) and its not something that you can just hold jump over and over to beat. Yes, its actually a challenge world. Great job Matt, it was a lot of fun in high school making Mario worlds with ya!