Last week, Coke unveiled its Facebook Timeline, and challenged fans with little puzzles to keep them engaged. One by one, the marketer released little riddles, that, if solved, led you to destinations that provided fun-filled digital treats. This one, FallingDominoes.com, is particularly delightful, providing a glorious 40-second display of toppling colorful tiles--without the worry of cleanup.

The first two presented the crackling flames of ABeachBonfire.com and fun bubbles you could blow with your computer mic on BlowingBubblesintheSky.com. Agency W+K Amsterdam calls the mini-sites "little islands in the internet where fun, unexpected things take place." Coke also just debuted its latest puzzle--with the following riddle:

The opposite of a frown, Turns a bad day upside-down. // There are more than a million, // And less than a trillion. // So many people with so many styles,// You can be part of the O _ _ B _ _ _ _ _ _ S _ _ _ _ _ .com