Explanation on types of sales:
Offerwall sale: you can earn free gold / diamonds in the game via the offerwall. These offerwalls are provided by partners (Tapjoy, Getjar, SuperSonic) and change on a daily basis. During an offerwall sale, you will get DOUBLE gold / diamonds.
Item sale: we select buildings / items in the game that can be build at a high discount during the item sale. Every item sale, other items are on sale.
Gold, Cash, Diamonds sale: get DOUBLE the amount for a limited time.
Expansion sale: buy expansions at a huge discount for a limited time.