The game launched with four gameplay modes, those being: Turf War, a multiplayer mode playing similar to Regular Battles in previous games; Anarchy Battle, a multiplayer mode playing similar to Ranked Battles in Splatoon 2 with a group of rotating game styles; Salmon Run: Next Wave, an updated version of the co-op mode introduced in Splatoon 2; and Return of the Mammalians, a single-player campaign focusing on the new Squidbeak Splatoon member Agent 3 as they deal with the onset of Fuzzy Ooze, a substance that bestows mammalian traits onto creatures that touch it. After launch, a fifth mode was added as DLC making up "Wave 2" of the Expansion Pass, Side Order, a single-player campaign focusing on Agent 8, returning from Octo Expansion, as they take on a mysterious tower called the Spire of Order.
