Audiosurf
In the game you pilot some sort of hover vehicle down a rack generated from a music file of your choosing. The style of music will effect the difficulty. For example slow songs will be easy, but the total points able to be gotten from that song will be low. Fast or louder songs will be faster and harder, with more points able to be scored. There are 14 different characters so choose from. The characters are divided into three difficulty levels and each has its own unique ability. (Eg, Eraser can erase blocks of one colour from the board).
The goal of the game is to score points by collecting colored blocks (called 'cars') and forming clusters of 3 or more of the same color. The more blocks in a cluster, the more points are scored. In the default color setting of the game, blocks which appear in hot colors such as red and yellow are worth more points, while cool colors such as blue and purple are worth less.
Osmos.
In the game you control a single celled organism. Game play consists of becomming the biggest cell or becoming huge by absorbing smaller cells or absoribing a particular cell(s). To do this you must move by ejecting biomass in the opposite direction to which you wish to go. The downside is that doing this shrinks you. So sometimes you must wait for collisions because going any faster would leave your cell vunerable to the very cell you wish to absorb! 9It is possible to slow down and speed up time, so it's not boring) In the game most other cells are quite content to just sit there. In fact, you exhaust consists of these cells.
However, there are some cells that will move around, using the same means of motion as your cell. These vary, from the Bio-Phobe, who will flee from anything bigger than it (which makes it more vulnerable, since faster motion will inevitably make the cell smaller) to the Neophyte, which will actively seek out smaller cells to absorb them. There are also many other cells, like repulsor, which pushes all cells near it away, to the anti-matter cells that cause all matter cells to shrink.
At the beginning of the game there are 4 levels, the introduction level, which has 2 stages and the first 3 levels, each with 3 stages. the second tier levels are similar to the first, but harder. There are 3 times as many 3rd tier levels that second tier levels. The 3rd tier levels take one of themes of the 2nd tier levels and expand greatly on it.
Game game also has a great soundtrack and the graphics are astounding.