Here's a video I've made for those who might find the Superflat Custom codes confusing. The video explains how to create each layer of block type and to input your own biome choice. The video is recorded in version 1.4.5 but I will be updating the Block/Biome ID lists as Minecraft is updated.
Superflat Preset Code Explanation - http://www.minecraft.../wiki/Superflat
Preset codes are broken down into 4 parameters seprated by semi-colons.
-> A ; B ; C ; D
A is version type, which seems to always be 2
B is block types and layer heights
C is biome type
D is structures and world generated items such as lakes, groups of trees, villages
The Classic Flat example shows this code:
Breaking this down, we see that
- Parameter A is 2
- Parameter B is 7,2x3,2
- Parameter C is 1
- Parameter D is village
This means the first parameter puts the coding of the preset to "version 2".
The second parameter has a 7, which is the block ID number for bedrock. Since a single 7 is written, one layer is added to bottom of the world. Next we have 2x3, which means there are 2 layers of block ID #3 - which is Dirt. Finally, the top layer is block ID #2 - which is grass. These layers stack on top of each other, so the player will spawn on the top of the highest layer listed.
The third parameter is the biome type. In this example, biome ID #1 is used - which is Plains. Biome types affect grass and leaf colour as well precipitation, structure generation of things like villages, temples, etc. So if you never want rain, you could make it a Desert biome, since rain does not fall in the desert. If you want Ocelots to spawn, you would need to choose the Jungle biome in your preset code.
The fourth and final parameter is the structure(s) allowed to be generated in the world. For Classic Flat, they have listed "village". Since it is the Plains biome, a "Plains" type village will be generated. If you change the biome type to Desert and include a village, the "desert village" will appear even if you do not include sand.
Be warned! Some block items will crash Minecraft if you preset an entire Superflat layer.
Known crashes from my personal examples are placing Wheat (Crops ID #59) on anything other than Farmland (#60), Side Signs (#68), Skull Heads (#144) to name a few... Redstone items, like torches and lamps can be listed as "off" or "on" but when they load, the game will change their state to what is proper.
Have fun and experiment. See how long it takes to mine through 100 layers of Obsidian (#49) or create a 1 layer thick world of Sand (#12) and watch the whole layer drop.