Otomata is a generative sequencer. It employs cellular automaton-type logic to produce sound events. And by sound events, I mean groovy tunes. It is not precisely a game, but is is very cool.
Each alive cell has 4 states: Up, right, down, left. at each cycle, the cells move themselves in the direction of their internal states. If any cell encounters a wall, it triggers a pitched sound whose frequency is determined by the xy position of collision, and the cell reverses its direction. If a cell encounters another cell on its way, it turns itself clockwise.
This set of rules produces chaotic results in some settings, therefore you can end up with never repeating, gradually evolving sequences. Go add some cells, change their orientation by clicking on them, and press play, experiment, have fun.