Classify <a href="http://www.galaxyzoo.org/">Galaxy Zoo</a> subjects. Official approved by the <a href="https://www.zooniverse.org/">Zooniverse project</a>. Asks you questions about a picture of a galaxy, with each question depending on the previous question. This "Citizen Science" helps astronomers to analyze the huge amount of images of galaxies provided, for instance, by the Hubble Space Telescope.