Super Mario Legacy is a traditionally styled platform game inspired primarily by Super Mario Bros. 3 and Yoshi's Island, and is the result of many years of development.
Features 75 challenging stages, colourful graphics, and a ton of ASM enhancements, including a game difficulty option, multiple midway points, hundreds of custom blocks and sprites, and utilization of the SA-1 chip to power features that would otherwise be impossible.
Note: I played this hack on expert mode and I'm not familiar with the normal mode, so some of my complaints may not apply to normal mode.
First off, a fair warning to anyone thinking of 100%ing this hack: it's a huge undertaking. Besides the sizeable exit count, each level is fairly long on its own (usually two or more midpoints) and a lot of careful investigation is involved.
It's clear that this hack is a labor of love that has had a lot of time and effort put into it. However, I personally couldn't enjoy it a lot, at least not as a 100% completion run, mostly due to my distaste for collectathons. The normal gameplay is mostly fine, although some parts of the game were pretty obnoxious, namely the desert world (pipe maze, smb2 sand level) and the postgame (autorun level, dry bowser fight).
The red coins and the moons, on the other hand, quicky became a chore to get. There are around 40 or so secret exits in this hack, and each of them requires you to turn over every stone in their respective levels. Some coins are insidiously well hidden (invisible blocks, offscreen coins, and that one palm tree that you could suddenly climb on come to mind). More often than not, I would reach the end of the level with one red coin missing and naturally it wasn't the greatest feeling. Something to counteract that would've helped a lot - for example, a menu telling you how many coins there are in each segment of the level. As for the moons, I didn't know I had to collect all of them for 100%, so by the time I found that out, I had no idea which moons I had already collected. I would've appreciated a moon flag on the overworld to better keep track of them.
To summarize, this is an alright hack, but I wouldn't recommend going for 100% completion unless you really, really like exploration.
From the looks of it, Expert mode seems to add more enemies in spots you would most likely see in later levels, removes powerups from certain blocks with the addition of Poison Mushrooms and you are given less time to complete the courses. Checkpoint locations and functionality seems to remain unchanged, keeping Expert mode fair.
I do like how getting all 8 red coins in one go spares you the trouble of playing the same course again just to get the normal exit. Speaking of Red Coins, the game does keep track of how many Flowers and Red Coins you had before hitting a checkpoint, so no worries if you die in a more painful course. There doesn't seem to be a Flower counter though, which is a shame for the inner completionist.
Nevertheless, this is a pretty fun hack that should be added to your collection.