App Store users have become smitten with What's The Word?, a free-to-play word association game from the developers at RedSpell. Currently, it's number two for iPhone and iPad, right behind the seemingly unstoppable Temple Run 2. Its popularity is suspect, no thanks to review bribery, but that doesn't necessarily ruin what is an otherwise fun puzzle game.

In What's The Word?, the developers throw four stock photos onto the screen that have one word in common. Your job is to figure out this word from a jumbled group of letters, where spelling it correctly results in a modest number of gold coins and the next puzzle.

Examples? A duck floating on water, a frog just beneath the surface, a child making his way to the ocean and a woman treading water. What do they have in common? S-W-I-M-M-I-N-G. In yet another, there's a paper airplane, along with three images of origami. Answer? F-O-L-D.

Keep in mind the answers aren't necessarily this obvious, which is where the hint system comes into play. Amass enough coins normally and/or through in-app purchase, and you can remove letters (359 coins), reveal a letter (239 coins) or add one more picture (239).

The catch? It takes quite a while to afford the cheapest options, though RedSpell will award you with 250 coins for reviewing the game. A shady practice we don't approve of, but the option exists should you choose to use it.

This aside, there's no denying the game's appeal. What's The Word? is a challenging iOS title ideal for solo players and couples. Considering the developer's commitment to adding new words and making tweaks, there's a great chance we'll continue to see this app in the top free category for weeks to come.