So I finished the demo, here are all the bugs I managed to find (besides the UI thing):

-   When loading any save file that's during an investigation section, the 'files' thing at the top is automatically shown but is all empty. It can be hidden by clicking on the 'files' button, which shows it again but as it should be this time. This doesn't happen if the save file is on a dialogue part though.
-   During the 2nd puzzle room, when the 'Vending machine costs removed from notes' message appears in the top left, the note doesn't actually get removed.

All the other bugs I found happen after loading a past save, probably because some of the game information is being saved in renpy rather than in the save file.
-   When loading to the 2nd puzzle room and investigating the vending machine from a save where I already collected some money, the 'costs' note displays the amount of money I collected in the future rather than being reset to $0.00. This doesn't let me buy anything, it's only visual. Also it changes to the correct amount after I get any money.
-   The hanging key has a similar problem where after reloading from a save where I cleaned the key to one before doing that, the dirty key has the icon and description of the cleaned key. However it functions as it should - it can't open the door until it is cleaned.
-   Notes duplicate when investigating them after loading a puzzle room #2 save. This happens no matter where the save is loaded from (before, after, or the main menu when first booting up the game). For example, investigating the vending machine even thought I already looked at it and got the note from it in that save. This is also true for the hanging key and probably other places where a trigger to give the player a note is.
-   The 'key not automatically getting cleaned' bug seems to also happen only when loading a save, but it requires a certain sequence of events. Which I tried to figure out but the bug is kinda irregular. The only times I think it happened for me was when loading a save that is after having already gotten the key down from the ceiling. Then when filling the bottle at the drip place, the game doesn't recognise that I have the key in my inventory and doesn't automatically clean it - the dialogue is the same as when filling the bottle before getting the key. If I load a save from around the beginning of the room and do it all in one go, everything seems to work fine.

And an extra thing, but not exactly a bug: It's possible to do the 1st puzzle without finding out people's birthdays (e.g. someone reloads their save to the beginning of puzzle room #1 for whatever reason, already knows where to put Serena's 0 in, so doesn't talk to people to get their birthdays). This means they never appear in the 'Profiles' menu. It might be good to have these perma-unlock and not be tied to the save (unlike all the stuff in the bugs above, which probably should be confined to the save file :p )

Anyway, having now finished it properly, I really enjoyed pretty much everything about the game! The writing is really witty and polished, the characters are interesting and varied, the art is great and the puzzles are engaging without being too difficult. I do have a few nitpicks here and there but it's a WIP so of course it's not gonna be perfect. I think this post has gotten long enough so I'll stop rambling now lol. If you ever want any help with anything in the future tho, I'd be happy to. ^ ^