iPhone games that you can play with one hand are a dying breed. It seems like flashy graphics and complicated controls are all the rage these days, and playing a game with just one thumb is a rare treat. Symmetrain is just that kind of treat.
You know those old "spot the difference" puzzles, where you have to compare two drawings and figure out what changes from one to the next? That's essentially what Symmetrain is, though instead of comparing two static images, you need to spot the differences between the scenery on one side of your train and the other.
Everything needs to be symmetrical -- hence the name, of course -- so if you see a spot where a tree should be, you need to tap that spot to score points. Alternatively, if you see an object that is not duplicated on the other side of the tracks, you can tap that object instead of the blank space. Either way, the points are the same.
You are penalized for missing things, which isn't much of an issue early on. After a while your train begins to pick up speed, and that's when things become a bit more difficult. With less time to compare the objects speeding past, both spotting and tapping the differences becomes much more difficult. It can get a bit frustrating when you can see your mistakes coming but can't react quick enough to avoid them, but the rewarding feeling you get for clearing a section perfectly is worth the occasional feelings of rage.
There are several trains to unlock, and each one performs differently and travels through a specific area, so there's plenty of content here to keep you busy. The simple controls are easy to learn and there's really no learning curve here, so you can jump right in without worrying about being uncomfortable.
The hand-drawn art is visually pleasing and the soundtrack is both relaxing and memorable. There's nothing particularly flashy about the presentation, but the important thing is that it's fun, and Symmetrain nails that aspect without issue. For US$0.99, it's a great one-handed game that is perfect for all ages.