These, you are told, are places to use objects . Problem is, the game is sometimes too complex for it. The cursor change that indicates this is sufficiently unobvious that I didn't figure it out until after I'd finished the game. And the final puzzle, while a brilliantly clever piece of game design, just absolutely doesn't fit into the interface. I knew what I wanted to do, but I stumbled through doing it by pure trial and error.
Hotspots appear and disappear at random.
Navigation stops working. You have to use an inventory item on a room feature, but a closeup view of that feature turns out to be the one view you can't use the item on. A wall panel stops working and then starts again. In fact, none of that sequence really made sense. I clicked everything on everything else, and hoped that the protagonist would carry out the Clever Plan that the designers had come up with.