Bug (mild late-game gameplay spoiler)

[Malkavian]

At the second scene in the final nightmare, I got stuck. The only thing around the floating islands I could click was to zoom on the fountain island, then on the fountain statue's hand. I had two car mirrors, a hammer, and an air freshener, none of which can be used on the hand, so I was confused as nothing else was possible. I spent a half hour carefully hovering over everything with the cursor, both on the zoomed-out screen and the close-up of the fountain island, nothing. The map greys out completely so you can't go back a scene either.

I gave up and clicked hint, which I really didn't want to do; immediately afterwards, an inspect magnifier icon showed up to the left of the fountain, in the stone doorway, which led to a puzzle (where I am now.) The inspect icon was absolutely not there before. I had assumed that spot would be something, it looked that way, but the cursor was normal all over it.

TL;DR - An inspect glitch meant I couldn't progress in the final nightmare until I had clicked hint.

[AlterDomoEgo]

I had a similar problem - rifle did not work, display moved down and didn't respond to the mouse. Solution (Maybe help someone later) - in game settings - enable window mode.