This pair of Flash games, hosted on Nobelprize.org, teaches you about the physics of liquid crystals while playing.
Crystallite is an action puzzle game, similar to Tetris, where you position the falling blocks by rotating them before fitting them in their place. Use the right and left arrow keys to position the blocks, and the up and down arrows to rotate the blocks clockwise and counter-clockwise respectively. The first part of the game is about filling up the play field with successfully completed rows, while the second part of the game is more Tetris-like where completing a row removes it from play. Click.
Mainstream is an action arcade game similar to Frogger, except with a bit more fluid movement (excuse the pun). The object is to get your car across the play field of moving liquid crystals within the time limit. This game is easy at first, then gets difficult quickly. Click.
Both games are simple and straightforward in design, while the implementations are excellent with a well-produced educational slant.