The battle system in Paper Mario: Sticker Star returns to the ways of old, to the turn-based battles in the first two Paper Mario games. The enemies must be attacked and defeated in the order they appear from front to back. In order to attack the second enemy, the first one must be defeated unless the attack affects more than one enemy. Mario's attack commands consist of single-use stickers found in the world. Mario only gets to use one sticker per turn by default, but he can increase this up to 3 using the Battle Spinner.
In the world around Mario, he can discover health upgrades and new stickers, but unlike the previous games, these mechanics do not involve an explicit level-up/experience system. Mario will become stronger as the game progresses, but the change is never made explicit to the player other than mathematically through increases in damage dealt in battle and the ability to one-hit defeat weaker enemies without initiating a turn-based battle sequence.
As with previous entries in the Paper Mario series, Sticker Star employs the use of timing on both attacks and defense. Pressing the "A" button at the right time when attacking or defending, will allow Mario to inflict more damage or receive less damage, respectively.
STICKERS
There exist two primary types of stickers in Paper Mario: Sticker Star: Battle Stickers and "Thing" Stickers, both of which are used in combat. Mario's Sticker Book has a limited number of pages based on the number of Royal Stickers (chapter-clearing items) he has acquired. He can only hold as many stickers as will fit in his Sticker Book, and if he runs out he cannot continue fighting and must run away if he is to survive. Additionally, an element of planning goes into filling the Sticker Book as stickers of each strength have varying sizes. Weaker stickers tend to be smaller, while the strongest stickers take up more space on a page.
Battle Stickers
Battle stickers range from different types of attacks, the primary varieties being jump-type, hammer-type, and item-type. Certain stickers have recovery effects, such as mushroom stickers. These range in potency based on their accompanying adjective: the weakest are "Worn-Out," followed by normal (no adjective), then "Shiny," "Flashy," "Big Shiny," and finally "Megaflash." Big Shiny stickers are twice the size of the previous types, and Megaflash stickers are twice the size of Big Shiny stickers. Battle Stickers are found nearly everywhere out of battle and can also be bought at shops for coins.
Thing Stickers
A major running joke of the game is the category stickers which depict many realistic-looking (and often household) objects which jarringly juxtapose the flat, cartoonish style of the game. These "things" which are referred to by the characters with alienating prose, can be summoned in battle with their stickers. The Things are acquired as items first by Mario who must take them to the "Sling a Thing" areas in the game to convert them into stickers. Once this is done, he can use them in or out of battle. Like battle stickers, they vary in size, and the larger ones tend to be more powerful. On the whole, however, Thing stickers are far more powerful and specialized than Battle Stickers. Finally, it is worth noting that Mario may only carry one Thing or Thing Sticker of its type at any given time. Things used up can be bought back from a "hidden" vendor in Decalburg.
THE BATTLE SPINNER
The Battle Spinner is a slot machine that Mario can use to get rewards during battle, such as health, coins, or attack boosts. If he gets a double match, he'll get one extra turn, but if he gets a triple match, he'll get two extra turns plus the jackpot bonus of whatever he has matched. Mario is able to spend 3 coins once per turn in order to use the Battle Spinner. If for some reason Kersti is not around, Mario cannot use the Battle Spinner.
