CastleVille: Play Bubble Safari for free Exploration Crystals

While Ruby Blast is the new hotness on Facebook and, Zynga is hoping that you'll still play Bubble Safari, the company's bubble-popping adventure on Facebook, and it's willing to pay to make sure you do. If you're a CastleVille player, there's a new promotion available to you that will allow you to win up to 25 Exploration Crystals for reaching different stages in Bubble Safari.

The Exploration Crystals are given out in three waves, meaning that you'll need to continue playing Bubble Safari for a lengthy amount of time to actually win all 25 of them. You'll earn batches of Crystals for reaching Regions 2, 3, and 5 in Bubble Safari, which sounds deceptively simple. Factor in the fact that each region contains multiple levels, and that you'll be limited by energy use along the way and you have a promotion that's much easier to complete on paper than in practice. Still, if you're up to the challenge, know that you'll have ample rewards waiting for you in CastleVille when you return.

What do you think of this cross-promotion between Bubble Safari and CastleVille? Do you play Bubble Safari because you simply like to, or just to complete cross-promotions like these in other games? Sound off in the comments!