In Foldit, the isosurface can be displayed using the "Show Isosurface" view option. (The advanced GUI option is required.) The Foldit isosurface is a translucent cloud colored in shades of red and blue, which is related to hydrogen bonding. The blue areas means there are hydrogen bond donors near the surface, and the red areas mean there are hydrogen bond acceptors near the surface. The isosurface can also be used to help determine how multiple protein units fit together, for example in a symmetry puzzle.