LSD Dream Emulator has a unique type of gameplay. It has no clear objective. Here is an exerpt from Wikipedia about it:
"In LSD the player navigates through a psychedelic dream world. The idea is simply to walk around and explore things in a dream environment. There are many strange environments in this world, and one way to travel through them is by foot. However, if the player bumps into walls or other objects in the game, they will be transported to another environment instantaneously through a system called "linking". Bumping into people, animals, or special objects usually results in a stranger dream.
Each dream can last up to 10 minutes, after which the player will 'wake up', when the screen fades away and the player is sent back to the game's initial menu. However, if the player falls off a cliff or into a hole in the dream, then the player will wake up immediately. There is a graph that appears at the end of each dream that keeps track of the player's state of mind; the states are Upper, Downer, Static and Dynamic, as referring to the environments and the general feel of the dream the player just went through. Past states may have effects on later dreams.
While the player walks through an environment, the surroundings may suddenly change. For example, eyes may suddenly appear on the walls and stare at the player. Even if the player visits the same place twice, it may look quite different - sometimes, the textures of walls will change to subtly different versions or new items will appear for the player to encounter. One may also encounter strange creatures while roaming around, including a celestial nymph flying through the air, a wild horse running through the prairie, or a huge man filling up an entire room.
The game is set in a first-person environment. The player may use the LEFT and RIGHT directional buttons to look and change direction, the UP and DOWN buttons to initiate or reverse movement and the shoulder buttons to strafe left or right. The player may also hold the X button while moving to run, the SQUARE button to look down and the TRIANGLE button to look up.
The number of "days" are kept track of. As the player progresses, the pattern on walls and the form of the player may transmute. Occasionally the player may come across a man in a gray trench coat and Hat, commonly referred to as the "Gray Man" or the "Shadow Man". He walks in one direction only. Getting too close to him will make the screen flash, the man will disappear, and remove the ability to recall the dream in a Flashback. Other such strange creatures are the "Abyss Demon", which lures the player to a wonderful sight just out of reach and then it suddenly appears from the cliff face and causes you to go to a new dream. Then in the house between two walls or on the second floor, there is a giant man in a bed, which will headbutt you and change to a new dream scape as well. These are among the most frightening sights in LSD.
After roughly 20 days of gameplay, a new option will appear in the main menu, called "Flashback". This mode lasts for only around 3 to 5 minutes versus the main game's 10. Flashback's purpose is to revisit locales and characters from past dreams. Due to the heavily random nature of the game, Flashback mode is often the only way to see an area with the same textures twice. Taking the same steps in Flashback as in the normal dream it is redoing will allow one to completely do over that dream."
-Source, Wikipedia. Link: http://en.wikipedia.org/wiki/LSD_(video_game)