I just played the Kobo Puzzle Game and received a 20% off coupon. No expiry was given, but I'm thinking it might only be good for today (December 14). I'll add it to the OP anyways. Let me know if anyone gets a better coupon or finds out the expiry. Looks like there will be different coupons every day.
The code is
holiday20dec14
Play the game
here.