Letterswirl is a word game for iOS that doesn't really rely on any of the standard word game conventions. The goal is to create a ring of letters in which every letter is used in at least one word. The letters have to line up in words all going the same direction, clockwise or counterclockwise, and letters can be used in more than one word.

The game is played in rounds, with a new, random letter appearing in the center at the beginning of each round. The player can swap one of the letters in the ring out for that center letter and then swipe along the ring to confirm the validity of words. Swiping around the entire ring to prove that all letters are used in words ends the game.

Letterswirl can be played solo or with a friend and is a universal iOS app. Its regular price is $1.99, but it's currently on sale for half off.