I just downloaded the game. I am running Windows 8. I try to play single player and the game freezes up and then quits. Any recommendations?

If you are running it on a laptop, or you have both a integrated graphics card and a AMD/NVIDIA one it may be caused by the game trying to run on the weaker graphics card. There is a technical support page on steam that may be of use to you. It can be found among the guides for Ring Runner on the steam community forums. It's called simply "Technical Support".