Like any other word game, Dabble gives the player a bunch of tiles and asks them to form words; this is fairly straightforward. Then the puzzle catch comes in: each round has exactly 20 tiles, from which the player must make exactly five words.
The field of play is a little pyramid of Scrabble racks that reminds you of the rules. One word must be two letters long, one three letters long, and so on to the bottom row, which holds a six-letter word. Many collections of tiles have more than one solution available, but learning to juggle all the words at once is the real trick. Since every letter can be used only once, it's entirely possible to make four satisfying rows of words and yet find "EROOGX" staring at you at the bottom (as I currently have), forcing you to rework the entire thing and jettison the other cool words you made.
Dabble [$0.99, iTunes]