WordScramble is an app where players create new English words from old ones by adding/removing/swapping single letters.
It has two modes: "standard" and "path."
In "standard" mode, the player maintains a hand of 10 new letters to pick from to alter the current word, and goes as long as she can stay alive.
In "path" mode, the player is given a specific starting word and target word, and a limited number of letters to use to reach the target word.