"I feel this article will be informative..."
A "Level Feeling" is a common feature of roguelike games that add a small chance of special themes being randomly applied to levels that play a little differently to normal.
Level feelings usually add special rules to the level, or unique structures and enemies that do not normally generate.
The name comes from how the special themes are commonly announced by exposition in roguelikes, as if the character has a vague sense of premonition about what they are about to run into.
Level feelings can stack; it is possible to have, for instance, a flooded Restless Dead level, or a dark Snake Pit level and so forth.
Spelunky Guy will always say something at the beginning of a level to indicate what level feeling is active, but will pause if there is more than one feeling before mentioning it.
"I can't see a thing!"
Terrain Features: The level will be in total darkness, except within a certain distance of light sources. Your vision in the dark is limited to a very narrow radius. The game helpfully generates a torch near the level entrance which is the most useful portable light source available. There will also be other light objects generated around the terrain that do not normally appear, such as unlit torches hanging on the wall, which can be lit by bringing the torch to it which will give up a few gold pieces. Additionally, traps such as Arrow Traps and Tiki Traps have candles on them that generate a small amount of light. Certain weapons and equipment, such as guns and bombs generate a brief but bright flash of light when used.
Unique Enemies: Scarab
Notes: There will never be more than one dark level per area.
Additionally, dark levels will not appear if you completed the previous level in 20 seconds or less, in order to prevent frustrating speed runs, though this does not apply to the Daily Challenge Mode. Entities such as Scarabs and the Ghost also provide slight sources of light, as well as the ghosts of dead spelunkers in co-op.
"I hear snakes... I hate snakes!"
Location: The Mines
Terrain Features: The level contains a snake pit, a long vertical shaft (with cubbyholes along the sides) filled with Snakes. The large amount of treasure that spawns here generally makes a snake pit worthwhile to explore, provided you have enough ropes or bombs to facilitate escape afterwards. A snake pit always has two rubies in the bottom of the pit guarded by five snakes and/or cobras. Falling from the top of the snake pit is usually fatal as the snakes will attack you while you are stunned, unless you land on one. A mattock will always spawn at the bottom of the snake pit directly underground, retrievable through the use of a bomb.
Unique Enemies: None, although snakes and cobras will always spawn in the vertical shaft located in the level.
Trivia: The phrase "I hate snakes!" may be a reference to Indiana Jones, who is known for disliking snakes.
"My skin is crawling..."
Location: The Mines
Terrain Features: Spiders, spinner spiders, and webs will appear with much more frequency, and there always will be an area of the level where four giant spiders will spawn near each other. Web nests are exclusive to this level feeling, found around the level attached to ceilings. They can be broken open with just about any weapon or projectile, or by using the whip. Most web nests have something cocooned inside that will fall out when the nest is broken, which can include a gold piece, a gem, a spider, and spiderlings, as well as a few random objects on rare occasions. The unlockable character, 'Round Girl' can be found in the level, assuming you haven't unlocked her before. Pots will not spawn on this level.
Unique Enemies: None, although four Giant Spiders will always spawn in an area of the level, hanging on the ceiling close to each other. Spiderlings are exclusive to this event from inside web nests, but are critters and so pose no direct threat to the player.
"The dead are restless..."
Location: The Jungle
Terrain Features: Mostly normal, except Gravestones will generate on top of the terrain which can be destroyed for loot. More bones and Skeletons will be found than usual, trees will appear to be dead, and Piranhas will be skeletal. The level has the characteristic mist of when The Ghost appears. There will be no Golden Idols on this level, but instead there is a chance of finding a Crystal Skull in a special structure. The Damsel can actually spawn inside the structure with the crystal skull, shown here . Once the Crystal Skull is taken The Ghost will appear suddenly afterwards. It is also guaranteed that there will be a grave marked 'Ash' on it, below which will be a shotgun buried. There is a chance a "King's Grave" will appear, which contains a valuable Crown and marks the entrance to the Haunted Castle.
Unique Enemies: Vampires and Jiang Shi are found on these levels in place of most enemies typically found in the Jungle, and piranhas will appear as skeletal. There will also be many more Skeletons than usual.
Trivia: The Ash Grave is a reference to the character Ash Williams from the Evil Dead series.
Bugs: In Restless Dead levels in which the Haunted Castle entrance spawns, it is possible, although very rare, for the Black Market entrance to spawn in the block directly above the Haunted Castle entrance. In this case, the Black Market entrance has no platform on which the player can stand on to enter, making it impossible to enter the Black Market if the block covering the Haunted Castle entrance has been destroyed.
"A wolf howls in the distance..."
Location: The Jungle
Terrain Features: There will be be a long castle on the centre of the level. At the bottom of the castle is the entrance to the castle, the exit of the level and a guaranteed altar. At the top left of the castle, a coffin ,which contains the unlockable character Van Helsing the first time is opened and a Hired Hand subsequently, awaits your Spelunker.
Notes: This level feeling always and only occurs in the Haunted Castle.
"I hear rushing water!"
Location: The Jungle
Terrain Features: A large portion of the bottom of the map is one huge lake. The exit tunnel is always found above the water level on an island. In the bottom lie gem chests, some being the same as Vault chests, with naturally spawning diamonds. The Viking Spelunker can be found at the bottom of the water.
Unique Enemies: Old Bitey appears in the large lake at the bottom of the map, along with a shoal of regular Piranhas.
The Black Market
"Welcome to the Black Market!"
Location: The Jungle
Terrain Features: The upper levels of the area are comprised of six shops in rows linked by ladders, and one shop unique to this area on the far right edge that sells the Ankh. The bottom layer is ordinary terrain.
Unique Enemies: None, but is populated with all the normal hazards in addition to 6 or 7 Shopkeepers with itchy trigger fingers.
Notes: This level is not applied randomly at the start of a floor, but the secret entrance must be located in area 2 behind solid terrain using the Udjat Eye and revealed with a bomb or a Mattock. Other level feelings can occur in conjunction with the Black Market (e.g. a dark black market). The ghost will still spawn as normal.
"It smells like wet fur in here."
'Location: The Ice Caves
Terrain Features: Unlike ordinary levels in the Ice Caves, the terrain of the Yeti Kingdom is much more continuous (although a large portion of it is ice), so the risk of falling to your death is not as great. However, fragile ice bridges with spikes underneath are common, and the loose blocks dropped by the Yeti King can block passages or crush you unexpectedly.
UFO Crash Site
"I sense a psychic presence here!"
Location: The Ice Caves
Terrain Features: Most of the space in this level is just empty caverns, with a large Alien Ship embedded in one of the walls, stretching horizontally across the level partially or completely. Turrets may spawn across the ceiling of the ship interior, and a jetpack can always be found hidden in the wall behind the Alien Lord.
"It feels like the fourth of July..."
Location: The Ice Caves, Level 3-4
Terrain Features: In either the top-left or top-right corner of the level there will be a conspicuous metal structure with thick walls and a tall vertical shaft. At the top will be the entrance to the Mothership, accessible either by climbing up the shaft from below or destroying the walls from the side.
Unique Enemies: None.
Trivia: For those who don't know, July 4 is Independence Day in the U.S. This level is a reference to the film Independence Day which is about aliens arriving on Earth.
"You hear prayers to Kali!"
Location: The Temple
Terrain Features: A deep pit spawns with numerous arrow traps and a pool of lava at the bottom. A Damsel and a Golden Idol can be found suspended above on a platform. Picking up the Idol causes the platform to disintegrate instantly, sending the Spelunker into the pit. This usually results in death, unless the Spelunker has climbing gloves or a jetpack to aid his escape.
The ground tiles underneath the lava pit contain rubies.
Unique Enemies: None, but a Damsel is guaranteed to be found.
The City of Gold
"I finally made it!"
Terrain Features: The area is not too different from a regular temple level, except all the solid tiles in the room are made of pure gold, which drop chunks of gold when destroyed. Additionally, there will be an enclosed room near the bottom of the level where the Book of the Dead rests, which is necessary to reach Hell. Picking up the Book of the Dead spawns Anubis II, who will occasionally spawn Red Skeletons.
Unique Enemies: Anubis II
Trivia: The City of Gold could be a reference to the Seven Cities of Cibola, which were rumored by Indians in the 16th century to be made of gold and filled with riches. This theory is supported by the fact that the cave which the Spelunker descends into is located in the desert, which is where the Indians said that the cities were located.
Level feelings can be an exploited in roguelikes like Spelunky with a technique known as 'level scumming'. This is done by generating a new level in the hopes of being given a certain feeling, and quitting and retrying if the feeling does not appear.
For instance, if the player wanted to start a game with an easy Jetpack, they would take the shortcut to Level 9 in the hopes of walking into a 'UFO Crash Site' level. If it turned out to be a regular level (or a 'Yeti Kingdom' level), they would take the easy way out and go through the shortcut again.
Scumming can also be done in the hopes of finding a shop, but since shopping sprees typically require a few levels of treasure to fund, this is not a very productive strategy for those not wishing to become the target of unrelenting geriatric vengeance.