The red guy maze in the big robot's brain was pretty frustrating. I had to screen capture the map and color code it in Photoshop. Yikes. But the green\blue\purple ball bearing puzzle on that same screen drove me batty. But as far as puzzles go, this was not nearly as hard as some games. The artwork and environments are so rich, it's just a pleasure to see each new screen. I love the backstory thought balloons too. And how cool is it to make a language-free game that could be played by anyone, anywhere. Smart move!