This game is kind of wonky, but what I've played is fun. Look, this is never going to be a commercial release and quite frankly, I'd be shocked if Nintendo doesn't force the dev to take it down. I'll list the problems with the title so you know going in what to expect. First, I spawned into the game with my legs squished into the floor. I think the dev built it like that (as Mario is pretty tiny compared to the world around him) but in reality my legs are just squished into the ground texture. It's not a problem, but it looks funny. Next, there is no tutorial and no explanation of anything. It wasn't a problem figuring out Mario's basic movement, but figuring out how to actually enter a level took me 5 minutes. Ultimately, I saw you have to push down a block to begin a level. It really isn't intuitive at all.
But once you begin, you're taken to areas where you can traverse maps to collect coins, bop enemies, and jump on flag poles. The actual gameplay is sort of fun and fine for a nice diversion. But make no mistake, this isn't anywhere near a commercial product--it's a fan-made "game" that is very rough around the edges.
That aside, the developer has done a fine job and the game is cute and fun for short periods. Check it out if you're so inclined--just go in understanding this isn't a highly-polished commercial product.