The only thing I would suggest to improve would be to maybe have a clock or something to indicate how long it can or might take to finish, because not knowing how long you're going to keep going on (even though I thought was immersive and pretty creepy) can be not as incentivising of players to keep going till the end. Maybe even having to shine the light on a wall to see a clock or maybe a small watch/ phone you can open up to see time progression would be a neat addition to have. And maybe the more the player excessively uses the flashlight or the phone, the grumpier Joy gets. (These are just my personal thoughts, I still think the game was awesome!)
Other than that, I think the mechanics were pretty spot on and solid and you did a great job on it. And also hope you're doing well, do take care of yourself and it was super brave and strong to use something that's been effecting you like that and make it into something this great. Really great job on it and do take care of yourself!