Fluidity is a 2D puzzle game with platforming elements, in which the player takes control of a large pool of water. The pool is moved by holding the Wii Remote sideways and tilting it left or right, which tilts the game world, while shaking the Remote will cause the pool to bounce upwards. The player is tasked with exploring the pages of a magical encyclopedia known as the Aquaticus, which has been infected by a dark substance called the Influence. The player must acquire Rainbow Drops, usually done by surmounting obstacles and completing environmental puzzles, in order to purge the book of the Influence.
The pool of water gains the ability to transform into two other states (a block of ice and a cloud of vapor) as the game progresses. The ice block can smash through barriers, weigh down switches and cling to objects, and the cloud can float around freely and expel gusts of wind, as well as electrify objects via a bolt of lightning. Some of the water can be lost due to damage from monsters and hazards, which results in a Game Over when all the water in reserve has been depleted, and can be restored by collecting water droplets.
Source: Wikipedia, "Fluidity (video game)", available under the CC-BY-SA License.