Jared Cosulich blogs about a fractions puzzle game he is exploring. He unravels each area with a series of screenshots and explanations, including the simulator, option set, goal, feedback loops, explicit content, appropriate challenges, editing / selecting levels and an escape valve:
The Escape Valve
The Escape Valve is simply a mechanism that makes it possible for a student to declare that a challenge is too hard and get additional help with it. This project will build out libraries that will make it easy to include a hint system that gives students one piece of the puzzle, allowing them to work their way closer to a solution. This technique only works if there are enough puzzles of similar difficulty so that a student can get hints on one and still be able to assess their proficiency by taking on another level of similar difficulty.