Splatoon is a third-person shooter set in a colour world. Players control Inklings, characters that run around and shoot ink with a gun but can also transform into a squid to traverse through the ink. The game is controlled through the GamePad with the left analog stick for movement. Next to regular means to aim, gyroscopic motion control, by tilting the device, is supported with the right analog stick to look left or right and the triggers to shoot with a machine-gun like weapon and throw large bombs. The game offers a large selection of primary and secondary weapons that can be equipped before battle. These include regular guns, rifles, bombs, grenades, a giant paint roller and items such as a shield, enemy detectors and inkstrikes. The game can also be played using a Pro Controller or Classic Controller, optionally in conjunction with a MotionPlus-enabled Wii Remote.
Shooting ink colours the environment and the areas that are covered in a colour can be used to traverse quickly as a squid by transforming. In squid form the character cannot shoot, but moves quicker, can hide and can also scale vertical surfaces and swim through grates. Ink ammo is not unlimited and is refilled by transforming into a squid. Characters can jump, also in squid form with a more powerful dash jump. Enemies shoot ink in a different colour that covers the environment as well. This slows down the characters in regular form and cannot be swum through in squid form, so they need to counter it by painting it over with their own colour. There is a limited amount of health that can be regenerated by seeking cover.
The game is set in Inkopolis that acts as a main hub. It offers access to different types of battles and characters that offer improved weapons and gear for aesthetic customization. By participating in battles experience is earned to level up along with a currency to buy new items. In the single-player part of the game Cap’n Cuttlefish asks to retrieve the Zapfish, Inkopolis’ source of power, from the Octarians. It consists of a series of levels completed by reaching the Zapfish at the end. In this mode only the default weapon is used, but it is enhanced and upgraded by collecting power orbs in the levels. The environments offer platform challenges and enemies to take out. Each of the 27 levels also contains a hidden scroll with lore about the game world. Levels are grouped in areas and at the end of each area a boss needs to be defeated. This is rewarded with blueprints called sunken scrolls that can be exchanged at a weapons shop for new options.
Next to the single-player campaign the game supports local one-on-one multiplayer matches in the Battle Dojo. Online multiplayer games are divided into regular and ranked battles where maintaining a high rank by winning provides more experience and currency. Battles are played as four-on-four matches with two teams each with their own colour. Regular battles have the Turf War mode. They offer matches of three minutes where each team attempts to cover more of the map in the team’s colour before time runs out. Ranked matches have Splat Zones, a King of the Hill game type where teams fight to keep a certain area in the team’s colour to get a counter to zero and win the match. If time runs out, the team with the lowest counter wins. Additional game modes (Rain Maker, Tower Control) were added afterwards as DLC. There are also special events only available for a limited time. By splattering opponents until they run out of health, they are sent back to the team’s respawn point. The GamePad can be used to access a map and instantly warp to a team mate’s location or to assist with aiming.
The game incorporates the Miiverse to post messages that appear in-game as graffiti on walls. Through Amiibo Splatoon sets additional missions can be unlocked, as well as additional equipment and a bonus mini-game after completion.