Sega is celebrating Sonic’s birthday by giving us a huge sale on all of their Android games. You can save up to 70% of Sonic CD, Sonic Episode I and Episode II. And Sega has just kicked off a contest where they will be away a Tegra 3 powered ASUS Transformer Prime. If you don’t win that device you’ll also be entered for a chance to win a Sonic pillow set, comic book or headphones. Click here to enter the contest.