Starting with a "ClueFile", follow a series of clues around a park or a neighborhood.
The ClueTrail app points you towards the next clue, giving you distance and direct towards that clue. Once you are within 20 meters of the clue, the clue is revealed. You then need to solve the clue and dial in the answer. Then ClueTrail will guide you to the next clue.
The ClueTrail app also lets you create and edit trail-files that you can send to friends and challenge them to solve.