The player controls the planet the LocoRoco inhabit to move the LocoRoco around. The player can also split larger LocoRoco into individual LocoRoco, and then recombine them. Splitting is required into order to fit through tight spaces and also solve many puzzles. (For example, smaller LocoRoco start singing when left idle for a while, which is required at the end of the levels.) There are 5 worlds to clear, each consisting of 8 levels.
The object of each level is to find and eat as many "berries" as possible to increase the size of the LocoRoco, to a maximum of 20. There are also "Pickories" and "Mui Mui" to find. The "Pickories" are used as currency for playing the minigames Mui Mui Crane and Chuppa Chuppa, while the "Mui Mui" unlock more minigames and music for the Loco House. The player must also be careful to avoid enemies, mainly "Burrs" (spiky obstacles) and "Moja", which can cause them to lose LocoRoco or even die if the last LocoRoco is lost.
The player can also collect "Loco House Pieces", which are saved and available from the Loco House minigame. They come in different rarities, rated from one star pieces (common) to three star pieces (rare). The player gets one for each "Mui Mui" they find in a level, but they can also be found lying around the level or obtained from other NPCs if a certain number of LocoRoco have been collected by that point. There are 144 pieces to collect; however 40 of them are special (each depicting a character from the game) and can only be obtained by finding all 20 LocoRoco in each of the 40 levels.
As well as the main game, there are several minigames included.Loco House
The opening sequence of the game shows the first LocoRoco you will have to take to high ground, the Yellow LocoRoco. But, as the plot develops, you will encounter up to 5 new types of LocoRoco, each with its own personality, voice and theme songs.Yellow LocoRoco The first LocoRoco of the game, the Yellow LocoRoco, is the image of the game around the globe and even inside the software, being the initial loading icon and wallpaper of the saved files. It vaguely resembles a Smiley and has a happy attitude for most of the game. It has a sole appendage on the forehead, turning into a double one from the moment you absorb a second LocoRoco. Its voice is deliberately child-like. The Yellow LocoRoco is voiced along the game by Alex Yamato Flaherty and in the songs by the young Japanese artist Melody Chubak. Its version of the LocoRoco Song is the main theme of the game, as well as on most of the TV commercials and websites. Also, the Yellow LocoRoco has two versions of its own theme music, Bu Bu Poroche, an instrumental one with choruses used for background music for most levels when you play with this LocoRoco, and a A Capella one for special events. Also sings Oreo - The Jungle's Awakening with the Green LocoRoco and Yoi Yore - Tossed By The Waves with the Black LocoRoco.Pink LocoRoco You find this LocoRoco in the second world of the game. The Pink LocoRoco is, at least in appearance, the only female LocoRoco in the game, not only for the association with the colour pink, but also for its characteristic lips. It is voiced by Leah, with a distinctive French accent in both vocals and songs. It has its own LocoRoco Song version, and its theme song is called Consepontowa. Its attitude and looks are happy and fragile. It has, although a little different from the yellow one, a sole appendage on the forehead, also turning into a double one after absorbing a second LocoRoco. It sings along the Red LocoRoco Dahi Dado Da - Lots Of Flowers and Doda Doda - The Snow Has FallenBlue LocoRoco Very much the baritone of the game, the Blue LocoRoco is the third LocoRoco you find in the game. It has skin colour lips, smaller eyes and a double appendix on top, turning into a triple one this time after absorbing a second LocoRoco. Its voice is given by Greg Irwin both in vocals and songs. It has its own version of the LocoRoco Song and his theme song is called Tajna Natata. Also sings Kuttetekaruna - Mojyas everywhere with the Black LocoRoco.Red LocoRoco The Red LocoRoco has distinctive weird looking eyes and a squiggly line for its mouth, with a set of three brown hairs on top, changing to five when merged. Has a very neutral accent, given by Hiroaki Takeuchi, with lots of highs and lows and a very strong r when singing. It has a version, like all the other LocoRocos, of the main theme, the LocoRoco Song, and its own theme music Panguraratta. Also sings Dahi Dado Da - Lots Of Flowers and Doda Doda - The Snow Has Fallen with the Pink LocoRoco.Black LocoRoco The Black LocoRoco is the fifth LocoRoco from the game. It has two distinctive fangs and a round and brown nose and a set of three thick hairs on the forehead, turning them into five when a second LocoRoco is absorbed. It has a bass voice provided by Jeff Gedert in both songs and vocals, with additional falsetto by Tomonobu Kikuchi in the choruses. Maintains a very serious rictus throughout the game, even in presence of the Moja. It has its own version of the LocoRoco Song and its own theme music called Zappudo Geron. Also sings Kuttetekaruna - Mojyas Everywhere with the Blue LocoRoco and Yoi Yore - Tossed By The Waves with the Yellow LocoRoco.Green LocoRoco The last LocoRoco you encounter of the game plot is the Green LocoRoco. With a sleepy and yawning look along the game, the Green LocoRoco has a set of four hairs on top, turning into seven after having absorbed a second LocoRoco. The voice provided by Cameron Earl Strother for the songs and Jack Merluzzi has a very strong Italian accent. This is also reflected in the theme music Bucho Mio, sounding very, at least, Mediterranean, accompanied with a Spanish guitar on the start and then, on a crescendo, with rock instruments. Also has a version of the theme song of the LocoRoco Song, with a lot of Italian flavor.
They all sing the final theme, Etoule Pucoratte, together.
A special halloween-themed demo has also been released on October 26, 2006. In addition, some retail stores received physical demos that carried a different level. There was also a beach themed demo released, and a Christmas demo was released on December 11, 2006.
Music plays a large part in LocoRoco, with each LocoRoco singing the song for the even numbered stages, and at the title screen. Three Mui Mui's sing during the odd numbered stages instead of the LocoRoco, and sometime pop up on the bottom left corner of the screen in the form of a choir in these stages. The LocoRoco have different voices depending on their color, varying in pitch and tone. Individual LocoRoco may also sing when they are split or merged together into one, producing choir-like singing or solo singing, respectively. The lyrics of the songs and "LocoRoco Language", a fictional language, were invented by Tsutomu Kouno to ensure that the music would be the same worldwide. The music was composed and performed (except for the vocals) by Nobuyuki Shimizu and Kemmei Adachi. The vocals are performed by Japanese children, as seen in one of LocoRoco's Japanese television commercials.
The LocoRoco Original Soundtrack has been released with 42 tracks from the video game on it.