Everything about this game is so well done and it was overall an absolute treat to play. Incorporates horror in an office setting in a perfectly atmospheric way.
What first drew me in was the art - the art style is super cute, so when the tone changes it really catches you off guard with the more creepy CGs. I love the variation in sprite poses, character expressions, and of course, the vast number of CGs you see throughout your playthrough. Truly a feast for the eyes. Then, there's the music. Every single track in this game encapsulates the floor's atmosphere absolutely perfectly. What really stood out to me were floor 4 and 8's tracks; the way they put a childish/glitchy spin on the main theme really makes those floors off-putting. My favorite thing, though, is the dialogue/characters. The humor they add is a great breather in between all the creepy stuff. Particularly love the recurring gag with the coworker giving us fake names, and also how there's special dialogue if you keep the rat alive!
The only criticism I have is that, like many others here, ending 14 did not activate upon a new playthrough (I did triple check I got all deaths), but I did read the dev's comment about what the ending entails so it's no biggie. One other minor thing is that you can't re-check the telephone number after closing out of its window, so I had to find it in the guide since I misread the first '9' as a '4'. But like I said, it's no big deal.
TLDR; Play this game, you won't regret it! Great art + great ost + great dialogue + great execution!