Most of the puzzles leave you hanging at the end. There is a direct beam going to a checkpoint, you change all possible colors of the beam through the most proximate filter, the beam is hitting the checkpoint......and nothing happens. It fails to activate it. This happens consisently with the last couple of checkpoints, and many times in the middle of the game. Some of the puzzles are worse than others in that regard. The authors of the game should check the puzzles to ensure that they actually work on a 3G iPhone (2.0.2. software) and provide an update soon!