Curiosity is a multiplayer social experiment. The game setting is a featureless and minimalist white room in the middle of which floats a giant cube made of billions of smaller cubes ("cubelets") and white, floating text across each layer, usually topic related (hashtag, notifications etc.), with small messages. Players tap the cubelets to dig through the surface of each layer and reveal the next layer below. The goal is to reach the centre and to discover what is inside the cube. Each layer, which has a distinct look or design, contains a clue as to what is in the centre of the cube. Each cubelet destroyed by a player awards them coins. Coins can be spent on tools that temporarily enhance the player's abilities, such as picks ranging from iron to steel to diamond that increase the number of cubelets destroyed with each tap, or firecrackers that can be laid on the cube in long strings to chain together explosions.
Source: Wikipedia, "Curiosity – What's Inside the Cube?", available under the CC-BY-SA License.