Did you know that light comes in little packages?

They are called photons. Photons act like particles.

In this game, five different kinds of photons will be shining on your Photon Pile-up "telescope:"

1. Microwave photons [blue]
2. Infrared photons [red]
3. Visible light photons [yellow]
4. Ultraviolet photons [purple]
5. X-ray photons [green]

Your game telescope is like the Galaxy Evolution Explorer, or GALEX for short. It is especially good at seeing ultraviolet photons.

In Photon Pile-up you get extra points for piling up three touching ultraviolet photons. These are colored purple in the game. You get fewer points for piling three touching photons of other single colors. But don't let the photons pile up too high! Keep the GALEX "telescope" spinning.