LiquidSketch is a puzzle game based entirely on simulated water. What makes it different from other such games is the simulation itself. It uses a different approach than most other games that trades some flexibility for very smooth and detailed fluid motion and realistic physics. The other distinguishing feature is that the water is colored and it mixes realistically. This allows you to see the motion inside the water in a visually nice way and is also used as a game play element.
The Puzzles are more based on physical properties of water than on Rube Goldberg machine scenarios. You might have to use pressure or the siphon effect in clever ways for example.
LiquidSketch also has a sandbox mode where you can experiment with all the game play elements however you want. There are already some cool experiments on YouTube!