From the site: "This app will load a (static Google) map of Barcelona and will superimpose a visualization of the current state of the bicing stations near the cursor. Every station is represented with a color-coded circle: the radius of the circle is inversely proportional to the distance from the cursor position (the closer, the bigger), and its color represents the amount of bikes available. If green, the station is full of bikes. If red, there are no bikes available. Possible tones in-between will give an idea of the amount of bikes."