One of my favorite mobile games (Dead Trigger) recently launched a challenge. You can find a code in there game and the first 10 to decrypt it will receive a T-shirt. Before I share the solution with anyone, I'd like to give you a chance to crack the code as well:
Good luck all.
P.S. Just got the confirmation I was lucky to be among the first 10 :-). I'll post a picture of the shirt as soon as it comes in.