Kenny got me into the iphone game "trainyard" and after beating all the puzzles and bonus puzzles on the free version and unlocking the bonus puzzles on the paid version, I can say it's a very good game.
Basic puzzles: get the red train to the red station, and the green one to the green station, but it gets very complex when you have to merge and split trains into different colors and have them share tracks and not collide.
The reason I'm posting it here however, is because after all this obsession I realized today it's very similar to how I work with the flame. It's hard to fully explain unless you've played the game a lot (because I don't think the analogy really applies until you're doing 10+ star levels) but there's something to the iterative tweaking and breaking of the train tracks I find very similar to solving a complicated compositing problem.
so get it. the free version is called "trainyard express" and is plenty challenging to get started.