Pikmin Underground

Pikmin Underground is a fan-made concept for a Pikmin game created by Soprano. The game takes place almost entirely underground, in one large interconnected cave system. The game has a darker tone than other Pikmin games, with a gloomier atmosphere, more frightening enemies, and several deep mysteries as to what is going on with the planet it takes place on.

World design
The vast majority of Pikmin Underground is set underground, in an enormous network of caverns and tunnels, connected horizontally and vertically. There is no day-night cycle. While there is just a single network, there are multiple 'cave biomes' throughout it, with various themes. Scattered around the map are a few 'home' sites, where underground Onions can be found. These are different from regular Onions in that they are connected to the ceiling with strange cables that allow Pikmin stored in an Onion to be taken out of another Onion elsewhere in the world. The shape of the map is roughly conical, with the upper layers being wider and the lower layers narrower, converging to a single room at the bottom of the world. The map is not divided into defined layers, and vertical movement is made through slopes, holes, geysers, and even some mechanical ways of moving between rooms.

The only above-ground section of the map is The Surface. This is a desolate brown wasteland area, with constant storms and wind blowing dust around. The only playable terrain here is a large featureless flat plain, surrounded by small walls to stop the player leaving, with some low mountains beyond. A hole leading underground is near the edge of this circular area. There are no enemies or items here so there is nothing to do, but it is the site of the crash-landing at the start of the game and the final boss fight at the end.

Story
A Hocotatian explorer (unrelated to Olimar) is on a leisurely exploration through the galaxy when they lose control of their ship and crash-land on the planet. Their ship is wrecked, and with nothing else to do they walk across the featureless plain of The Surface until finding a hole in the ground. Jumping down the hole takes the explorer into the first underground room. In this room, they find an Onion, which presents the first Pikmin: a single White Pikmin. After a tutorial, the explorer is able to head down into other rooms, where various combat encounters are found. They later find scrap materials, which are necessary to rebuild the ship. These can be carried to the nearest home site, but there's no way to get them up to The Surface. They also find crystals, which are a notable item, but their use remains mysterious. Over the course of the game, the explorer heads deeper and deeper into the cave system. Other Pikmin types, Onions, and collectibles are found. Eventually, at the very bottom of the cave system, a dark secret is found, and it relates to how the ship crashed in the first place. Once this is activated, returning to the surface will reveal the final boss of the game.

Structure
Pikmin Underground would have a partially non-linear structure, as the player would be able to choose how to explore through the cave system. It would be possible to find the regions of the map in various orders. The game would place less of a focus on collecting things and time management, and more of a focus on combat, puzzles, navigation, and atmosphere. There would be 5 Pikmin types: White Pikmin, Yellow Pikmin, Blue Pikmin, Glowing Pikmin (they have mushrooms on their heads that glow in the dark, illuminating really dark caves, and are resistant to fire, which makes them glow brighter), and Burrowing Pikmin (which are able to dig through certain types of rock). These types have more broad applications than in the original games, to allow for more diverse puzzles. (I'm not totally sure about these types, nor the colors of the new types.) These are all accessed from the same Onion, and there are multiple Onions in the cave system with the same Pikmin reserves. There is a limit on how many Pikmin can be outside of the Onions, but it would probably be higher than 100.