Mini Ninjas is a 2.5D side-scrolling auto-run platformer based on the original Mini Ninjas game. The player gets to control Hiro and his ninja friends to retrieve an artifact that has been stolen by a dragon. Hiro runs automatically and attacks samurai warriors with his sword by himself when colliding. Tapping is used to jump, to avoid obstacles (rocks, spikes, fire ...), to attack enemies in the air, to wall run (by tapping and holding) and to get on platforms. The game has an endless environment with variations in design and enemies for each run. As soon as Hiro is hit, the game is over and the level needs to be restarted.
Along the way Koins can be collected, the currency in the game. These can be spent in a dojo to unlock additional outfits, potions, kuji spells and animal pets. Outfits consist of hats, robes and weapons to alter the character's appearance. Potions are obtained by spending Koins and collecting ingredients during runs to craft the items. They act as boosters with a one-time use that last an entire run. They include a death banisher to continue after dying once, a refill for ki energy, a booster for kuji spells, the kuzanagi longsword as an improved weapon and the lucky Koin charm with more value for collected Koins. After equipping them they are shown near the top of the screen where they can be tapped to use them.
By defeating enemies and freeing animals from cages during a run, a ki energy meter is filled slowly. When full a kuji spell can be activated, such as a tornado boost to travel a large distance, a lightning storm that kills all enemies for a while, an asteroid blast, a spiritual shield etc. For large amount of Koins pets can be unlocked. They allow the character to transform into an animal such as panda bear, a fox or a crane with new abilities. There are different types of objectives to complete, presented as missions. They provide experience and level up the character to achieve a new rank.
After running a certain distance Hiro will encounter one of his friends. They are rescued by freeing them from a cage. They act as an extra life as Hiro is replaced by them until they die. The strong Futo can smash through rocks with his hammer and does not need to dodge them through jumping. Suzume has the Koin madness skill to collect more of the currency and attacks with her flute. Kunoichi is able to jump and glide through the air using her staff, making it easier to avoid obstacles.
It was originally released as a commercial game, but was later turned into a free-to-play title with in-app purchases for additional Koins and bonuses. It does not include an energy / stamina system or in-game advertisements.