Interesting use of the theme!
Having to micromanage between many different applications is quite a literal use of the limitation, but I like how you added a bit more to it by having it be for controlling organs, rather than the usual desktop stuffs.
I think that the best thing that this game does is the few windows that have interactions that work with the window itself, like having to shake the stomach window to do its action. Things like this work really well at making unique mechanics and ideas with a limitation and presentation like this.
Part of the game was to be able to organize the mess of windows, and have to shuffle them around to get to different things. But I found it a bit too difficult to move them how I wanted, since sometimes it felt like other windows were overlapping them, even though they were visually separated. This may be a hitbox size issue? I also found it a bit easy to eventually rearrange the view so that I had all important information on my screen, and didn't need to worry about moving everything.
I think that using more of the windows and usual OS interactions would be great to add to this game. Having to think about where you place things and such. (Like placing the heart monitor to the right is bad since then you cannot see the bar that shows up when you use it) Maybe have some features to close and open tabs, or change the size of the windows to effect what is inside of them. Giving the player more actions to do with the windows themselves I think is the best route to take for this game.
The only other thing that I would have improved is the tutorial, I did like how your tutorial was more than just text and involved actually doing the actions. But, when a game has many complicated features it can be hard to tell the player what to do. When a player is given a mountain of text and information it can be very overwhelming, and often times players will just say "I'll just figure it out." and ignore the tutorial, leading to very bad gameplay. Although I do think that this game is pretty easy to grasp compared to some of the other "wall of text" games I've played before, if you add more mechanics it will quickly become impossible to do things on the first pass.
Likely the best way to teach the player would be to introduce the windows as the game goes, only add things once they prove they know what they are doing. Think about how Papers Please doesn't throw all of its mechanics at the player on their first day, but adds them all up over time.
The visual style itself is very nice! I like the vaporwave aesthetics.
It seems like the brain had no limit to buying things? I could just continue to buy things from it and it would just go into the negatives. Maybe forgot to add a check for that? :)
Good job!