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 bedrock, two dirt layers, and one grass block layer on top. Three buttons, "Add Layer", "Edit Layer", and "Remove Layer", allow you to completely change the world, including filling all 256 layers with something. Currently (as of 12w37a) the add and edit options are not yet implemented. There are 7 presets included in these options.

Presets are also 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.

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.

Trivia

 * The volume of an entire Superflat 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 seem to spawn more frequently on Superflat worlds than normal worlds, due to the fact that the entire world generates as a Plains biome.
 * Before 12w25a, Slimes spawn in huge numbers in Superflat because they are only four blocks away from the bedrock layer.
 * In creative, if one digs through bedrock in the right place but does NOT fall in, the moon/sun can be observed at noon/midnight respectively.