Few of us will think much about the liquids we use. We fill our vehicles with oil and gas, use water to brew our tea, pour detergent into the necessary appliances for clothes and dishes, and dump drain cleaner down the tubes. We take it for granted that these fluids flow into the assortment of everyday items they're used with. In basic terms, it's nothing more than the simple assembly of elemental cause and effect.
But suppose for a minute that there exists a secret life of liquids, a journey that occurs whenever we perform one of those most basic of utilitarian actions like pouring soap into a dishwasher, or even when, say, rainfall flows into a drainage pipe. Where does that liquid go, and how does it get there?
This is the idea behind Puddle, which follows various liquids through their own quests to arrive at their final destinations. The idea may sound familiar - WiiWare's Fluidity used a similar premise that let you control water in various states. Thankfully, Puddle has none of Fluidity's ridiculous narrative elements.
Of course, in real life the unseen world of liquids isn't interesting. The boiling water goes from the pot to a teacup. Gas and oil flow into appropriate tanks or reservoirs to help power a vehicle. The soap is distributed throughout the dishwasher once it's turned on. The whole process is usually taken care of by gravity and engineering.
This isn't how Puddle operates, of course. The design itself is based entirely around mastery of some very impressive physics - all you do in this situation is tilt the screen at a left or right cant and use gravity, momentum and inertia to navigate your puddle through increasingly taxing obstacle courses.
The game starts when you knock a coffee cup over in a lab - the liquid is then (presumably) purified into a clean state, which you have to guide through a complex series of lab courses.