Nightmare Circus is an action-adventure game where the player takes on the role of a Puppeteer trapped in the Nightmare Realm. As a member of a wandering Circus troupe, you suddenly find yourself lost in an unknown land. You must fight enemies that wander lands, save your fellow troupe members that are also stuck within this realm, uncover the mysteries of the realm, and make it back to the real world.

The key feature in the game is the “Puppet String” mechanic. The player can use the puppeteer’s two puppet sticks as a weapon as well as use the puppet strings to launch the sticks. The sticks can then be pulled back and recalled to the player via the strings or the player can become a puppet and be pulled towards the sticks via the string. In combat, this enables players to launch range attacks and also maneuver quickly around the stage. The "Puppet String" mechanic can also be used to move around the world, such as scaling large gaps and solving world puzzles.

Another feature in the game is “Friend Assistance” where the player can employ the help of troupe member friends’ skills after successfully rescuing them from their Nightmare. Equipped skills will affect the properties of the player’s weapons, giving them special abilities. These skills will not only aid you in fighting against monstrous Nightmares but will also help you unlock world puzzles to venture further into the realm to uncover its mysteries.

Embark on an eerie yet whimsical journey through the twisted realm of Nightmares, traverse this mysterious land, unlock its mysteries to fend off monstrous enemies, and save your friends, becoming the bravest puppeteer the realm has ever seen.