I apologize in advance for repeating a rather common criticism, especially considering that this is the beta version, but still:
Mario horror game? Sounds interesting! Luigi's Mansion proved it could work! So where the hell is King Boo, then? I mean, the setting is a ghost-infested mansion and the plot is dead serious! King Boo would've fitted in perfectly as the main antagonist, and he's completely absent in favor of an OC.
In fact, Mario feels like he could've been taken out of the story and replaced with another OC and nothing would really change. A good, proven-to-work premise of a Mario horror game, and it's wasted by the fact that the only three characters from the franchise who actually appear are Mario, Luigi and Peach, and they basically play second fiddle to a bunch of OCs.
Also, I know you call it "edgy" and it was made to deal with health conditions, but the "edgy" content goes way over-the-top sometimes. It's Mario! Mario is meant to be funny, and silly, and goofy! Even Luigi's Mansion knows when to crack a joke! And he's expected to be taken seriously?
Again, art style's good, and it could've been a serviceable explorer horror, if it wasn't for the fact that it just had to have Mario basically making it a joke.