This is a datapack focused on making as much content as possible available in a superflat world. In my opinion, the core aspect that makes superflat survival unique is having to exploit what few structures spawn to obtain resources. To this end, this datapack increases both the number of structures that can generate in a superflat world and adds more ways to exploit them for novel resources. For anything that doesn't cleanly fit in a structure, by leveraging Minecraft 26.1's data-driven trades, the Wandering Trader is made to carry them.

Worldgen Changes

The datapack adds a new superflat preset. This gives you 64 blocks of air below bedrock, placing the bedrock layer at Y=0, same as you get from a superflat world originally generated before 1.18.

Biome Changes

The biome used is still the Plains biome like classic superflat. The only change made directly to the biome is lowering the temperature slightly: this allows snow and ice to form at the highest elevations, around Y=310 and above.

Structure Changes

This is the meat of the content: almost every structure is now capable of spawning in the Plains biome. This means:

Plains Village
Desert Village
Savanna Village
Taiga Village
Snowy Village
Pillager Outpost
Ruined Portal
Trial Chamber
Stronghold
Ancient City
Desert Pyramid
Jungle Pyramid
Igloo
Ocean Monument
Woodland Mansion
Trail Ruins
Shipwreck
Buried Treasure
Swamp Hut
Warm Ocean Ruins
Cold Ocean Ruins

Will now all spawn in the world. Additionally, a handful of things that are normally placed features (Desert Well, Amethyst Geode, Simple Dungeon) have been turned into structures and will also spawn.

Some of these structures generate beneath the bedrock, but don't worry! While some structures like Trail Ruins and Trial Chambers get bisected by the bedrock layer, others like Desert Pyramids and Igloos punch right through it, allowing access to the area underneath.

Mob Changes

Many structures have been changed to spawn additional mobs within their bounding boxes. All normally inaccessible mobs are made accessible in one of these places:

Desert Pyramid

Husk
Parched
Camel Husk
Rabbit
Warm Animal Variants

Igloo

Polar Bear
Fox
Goat
Llama
Stray
Cold Animal Variants

Jungle Pyramid

Parrot
Ocelot
Panda

Ocean Monument

Axolotl
Pufferfish
Salmon
Tropical Fish
Squid

Ocean Ruins

Drowned
Zombie Nautilus
Dolphin
Turtle
Nautilus

Swamp Hut

Frog

Trail Ruins

Wolf
Armadillo
Mooshroom

Note these are only the additional changes from the vanilla structures: any other normally-unobtainable mobs can already be found from one of the added structures.

Trade Changes

Lastly, a few miscellaneous organic items were added as possible trades for the Wandering Trader, including some that are already trades on Bedrock Edition:

Brain Coral
Brain Coral Fan
Bubble Coral
Bubble Coral Fan
Fire Coral
Fire Coral Fan
Horn Coral
Horn Coral Fan
Tube Coral
Tube Coral Fan
Bush
Glow Lichen
Pink Petals
Spore Blossom
Lilac
Peony
Rose Bush
Sunflower
Mycelium
Cocoa Beans

Between these additions and loot chests in added structures, all blocks and items should now be obtainable.

Miscellany

This is a project that started about 3 years ago, and was put on hold indefinitely until it could be fully realized as only a datapack. With Minecraft 26.1 making trades data-driven, that dream could finally be fulfilled.

The only remaining consequence of a hardcoded feature limiting the potential of this datapack is Woodland Mansions. They have a hardcoded minimum height they generate at (around Y=60), and as there's no way to change this, normal mansions cannot generate in this superflat preset. The mansions that do generate are all the same pre-generated layout, but each mansion does still have unique loot.

Superflat Survival+