Superflat



Superflat (sometimes called Flatlands) is a world type replacing the normal varied terrain of the Overworld with a thin flat layer of dirt.

The terrain consists of one layer of bedrock, two layers of dirt, and one layer of grass; the surface of the world is completely flat and at height y = 4, with the exception of NPC villages. Since the height limit (256) is unchanged, there is then slightly less than one-third more vertical height available to build above-ground structures as compared to a normal world. Mobs spawn as normal, including Slimes; however, there is no “Void Fog” as would ordinarily be caused by being close to the bottom, even for areas that are completely shielded from sunlight, whether in Survival or Creative mode.

Because of there being chests in villages, and villages frequently spawning near the spawn point, it is possible to use Superflat as a challenge map. However, the high amount of slimes makes this extremely difficult to an inexperienced player.

The Nether and the End generate normally; they are not flat, although there is no possible way for the player to travel to the end in superflat without using creative mode or a mod, as there are no Strongholds. In order to create a Superflat world in SMP, the level-type flag in server.properties must be "FLAT", instead of "DEFAULT".

Customization
In 12w37a, customization options were added to the world creation screen. Upon selecting "Superflat" in the World Type box, a new button appears underneath called "Customize". The customize menu starts out with the "Classic Flat" preset of one layer of grass, two dirt layers, and then bedrock underneath. Three buttons, 'Add Layer', 'Edit Layer', and 'Remove Layer', allow you to completely change the world, including filling all 256 layers with block types of your choosing. Currently (as of 12w37a) the add and edit options are marked 'NYI', to show they are not yet implemented. There are seven presets available, and provided you can understand the layer syntax you can still create presets of your own by entering the correct block IDs into the 'preset code box'.

Presets are shareable. As a preset is selected, a box on top of the screen has a code you are able to highlight and copy. Similar to how new worlds are shared through seeds, presets can be entered into this box to recreate someone else's preset.

World layer codes
At a future point there is expected to be some way of choosing block types merely by selecting them from a menu. For now, you must type in a correctly-formatted string of numbers.

Here is an example format string: 1;48,250x0,49;8

It consists of the following elements: 1; – world ID of some kind.
 * It seems this must currently be a number 1 followed by a semicolon. Further info TBC.

48,250x0,49 – comma-separated list of block IDs
 * These are listed from the bottom of the world upwards.
 * In this example, we have mossy cobblestone, then 250 air, then a layer of obsidian.
 * If you want multiple layers of a block type, give the number of layers, then an x, then the block ID. Hence 250x0 gives 250 layers of block ID 0, which is air.

;8 – biome type
 * The semicolon marks the end of the list of block IDs, then we have world's biome type.
 * Most default presets have a biome type of 1 for plains. This example uses biome type 8, for the nether.


 * Players will spawn above the topmost non-solid layer. This means you will tend to spawn under water or lava if that's what a world's topmost layer(s) contain.


 * If you want multiple instances of a single block type, put the number of repeats first, then the block ID. Hence 10x20 gives a layer 10 blocks thick of block ID 20. Presumably you could get the same result with 20,20,20,20,20,20,20,20,20,20


 * Entering a nonsensical item ID, such as flowers, grain or torches gives a layer of air.


 * Entering an invalid layer string causes the world to default to the Classic superflat layer set.

Resources that can be found in Superflat world
The resources below can always be found, regardless of the "Generate Structures" option.

The resources below can only be found if the "Generate Structures" option is enabled. These do not include trading with villagers.

Village chests may contain these items:

Bugs

 * If the player breaks the Bedrock barrier, the player can see that the Void has the same color of the sky while the player is above y=0, but looks normal (black) when the player is below y=0.
 * Superflat worlds may contain chunk errors that will generate default worlds.
 * If you overwrite a Superflat world with a default world of the same name, some chunks (and sometimes massive areas) may remain Superflat, though the grass color will change with the biome.
 * Water World spawns you on top of the dirt layer, making Survival impossible in a new world. Workarounds are either spawning in Creative and flying up, or editing the save files after world creation to move spawn.

Trivia

 * The volume of an entire Classic Flat world, not including villages, bonus chests, or air, is 3.6 million km3, and the world is composed of 3,600,000,000,000,000 blocks.
 * NPC Villages spawn more frequently in Classic Flat worlds than in normal worlds, because the entire world generates as a Plains biome.
 * Before 12w25a, Slimes spawned in huge numbers in Superflat worlds. This was because slimes spawn below layer 40, and in Superflat the entire world surface is only four blocks away from the bedrock layer.
 * In creative, digging through bedrock in the right place allows the moon and sun can be observed at noon and midnight respectively.