Urchin is an interactive program for Mac with a kind of ambient game mechanics. This minimalist game is small in scope with only about 30 minutes of gameplay. Move your urchin around using the arrow keys to eat the algae (phytoplankton) with its circular mouth. Through eating more algae your urchinesque thing will accrue layers. After eating enough algae you will enter a new phase of music and your urchin will change shape. The only threat is a jelly fish which is very benign, and there is no way to win. This 'game' is more about an audio visual environment and experience. Currently it is only for OS X 10.4 or higher but there will likely be a PC port in the near future. Just extract the urchin folder and click on the Urchin icon inside. If you experience no sound or loss of sound try restaring. The visual part of Urchin was developed using the Processing programming environment. The audio was created with the SuperCollider audio programming environment. Urchin is open source.