Ninjatown is a tower defense strategy game for the Nintendo DS, After the eruption of a nearby volcano, Ninjatown is attacked by hordes of devils, who are lead by Mr. Demon. The player takes the role of Ol' Master Ninja whose job is to defend Ninja Town from Mr. Demon and his hordes of minions, by building Ninja huts to stop the oncoming hordes.
There are squares along paths throughout the game where you can place your Ninja Huts, called lots. Once you build a hut, ninjas will spawn to fight Mr. Demon's waves of devils. The huts can be bought, and upgraded with Ninja Cookies, which are earned though killing enemies, or through a certain Ol' Master Ninja Power. Eventually, you will be able to purchase Modifier Huts. Each Modifier Hut gives a different bonus to the Ninjas who have huts near the modifier, such as boosting the attack of a ninja, the attack range, or something else entirely. Modifier Huts can't be upgraded, and affect all the Ninja Huts that are touching their square, be it directly next to or diagonally touching them.
You also gain things like Ol' Master Ninja Powers, used by earning happiness, which you acquire by defeating enemies. You fill up the Ol' Master Ninja's Cane, a bit and you can unleash a skill to aid you in battle. Most powers take up one or two sections of the cane, which has three sections in all.
Character Tokens are earned after every battle, starting at the end of the the fourth level, in the first chapter. Simply place them on the battle, and the varying four of them will affect the enemies in a negative way. They could slow down, stun, or even damage the enemy. There are other little things that occur in battle, such as the appearances of Feroshi the Dino Slug and Cannons.
Ninjatown supports 2-player multiplayer, although there is only one mode. In it, the players fight Mr. Demon's demons on their own separate maps. Each player has 10 health (1 health is lost) for every demon that gets through, and each wave, the player who kills all the demons slowest will lose 1 health.