You trigger these movies when you walk into certain areas or examine special objects, and for the most part, you can easily re-trigger them repeatedly in case you missed something on the first viewing. Some of them contain vital clues for progressing the game. Haunting melodies for the most part, of course. They add immensely to the atmosphere. Sound effects are as you might expect for a modern adventure.
Nightmares can be so deceiving.
I hope you were paying attention in algebra class. One particular mathematical puzzle in Morpheus had me scratching my head for hours. I knew all the information needed was there right in front of me, but I just couldn't put all the pieces together. Finally, when the solution came to me, I was absolutely delighted with the fruits of my endeavours. As with all adventure games, not every puzzle is a winner.