Mario, Peach, Toadsworth and several Toads land on Isle Delfino, where they intend to have some rest and relaxation. However, they find that the island has been polluted with paint graffiti and that the source of the island's light - its 120 Shine Sprites - have left as a result. All the blame goes to Mario because of a doppelganger being sighted defacing the island (a la Sonic Adventure 2). Mario is put on trial, where it is decided that he shall stay on the island until he cleans up all the pollution and restores the Shine Sprites. But just who is this Mario look-a-like? The titular protagonist will just have to get through the muck so he can see things more clearly.
Mario's abiities in Super Mario 64 have been carried over into Sunshine as well: he still sideflips, ground pounds, and belly slides with the best of them. Some improvements have been made; for instance, he now slides against walls before kicking off from them, meaning that the player doesn't have to jump at the very second Mario makes contact with a vertical surface. The big game-changer here is Mario's FLUDD (Flash Liquidizer Ultra Dousing Device) waterpack, which he wears like a backpack and uses to perform a variety of water-based actions: initially, he can spray water on enemies, graffiti and the like, as well as hover by firing water out from the bottom of his FLUDD pack; these can be switched from one to the other via the 'X' button, and the latter can be replaced later on with the Rocket Nozzle, which shoots Mario directly upward, high into the air, and the Turbo Nozzle, which propels him forward at a rapid speed by firing water from out of the back of his waterpack. When in water Mario's pack ca be refilled with 'R' as well. The FLUDD device has been criticized as a forced gimmick, but it really does invite quite a lot of unique platforming scenarios and keeps the game from being 64 all over again.
Just as the yellow 'C' buttons were used in Mario's previous 3D adventure, the yellow 'C' stick allows the player to rotate the camera seamlessly (rather than in large turns) by holding left and right and zoom in on and out from Mario by holding up and down; moreover, he can combine zooming in and out and rotating the camera by holding the stick diagonally. Finally, the player can view things from a stationary Mario's perspective via the 'Y' button.
The levels are large sandbox areas connected by a world hub (Delfino Plaza), as was the case in Super Mario 64. Though they all follow the tropical island theme, each one presents a unique stucture and visuals to vary the experience. Every now and then the player will come upon secret levels, which feature classic-style platforming courses that win the prize for most difficult parts of the game. Most of the time a 1-Up mushroom can be attained early on in each such level, giving the player a means by which he or she can attempt it over and over. The levels from the game involve a number of different platforming elements, though tightrope walking seems to be the most reoccurring. With FLUDD at Mario's environmental disposal, platforming that would normally be downright frustrating can be worked around (except in the secret stages, where Mario can't use it), while some feats that are just plain unachievable without the device are made possible, and, in fact, mandatory to collecting many a Shine Sprite. There are seven levels in all, each of them containing eleven Shine Sprites, the hub containing sixteen, three are collected at miscellaneous points, and twenty-four can be bought at ten blue coins each. By spreading blue coins throughout the game, the gameplay is extended as a significant number of stars are unattainable without collecting them. There are 120 stars in all, making this formula the staple for 3D Mario series.
Pervading throughout the game is a decidedly tropical theme, made no less involving because of the visuals and score. All of Isle Delfino is bright and vibrant, with detail that's leagues ahead of that present in Super Mario 64. The music is relaxing and evokes the same reaction from the player as one would expect from the music played while on vacation in Hawaii or the Caribbean. The resulting tone is much like a chill summer break.
Sandwiched inbetween the likes of Super Mario 64 and Super Mario Galaxy, Sunshine is often considered the lesser of the 3D Mario series. But even if that's the case, the game still has plenty of space below them to be quality in its own right. It brings its own gameplay and atmosphere to the table, the distance in time between 64 and Sunshine allowing Nintendo EAD to collect their thoughts and do something different from before. It's also politically correct, on the environmental front at least (nevermind Mario's steriotypical Italian accent). Almost as much time was spent before the release of the next 3D Mario installment, after which the ball for the series really got rolling in rapid succession.