There are times when you just need a light diversion that isn't too time intensive. Flow Free is a game that fits that need very well, but unless you pay, you'll have to put up with some advertising.
The well-designed interface is sleek and attractive. The object of Flow Free is simple and so are the controls. Your goal is to connect matching dots of color with a line, or pipe. The trick is that the pipes can't cross and you have to fill up the screen. There's enough strategy to make it interesting, but not so much that you can't play it on the bus ride home. To keep things interesting, you can play in "free play" or "time trial" modes. In free play, you can take your time to solve the puzzle, but the real challenge is the time trial, where your goal is to pass as many levels as possible within a chosen time frame, from 30 seconds to 4 minutes. You can also increase the difficulty by switching from the default 5x5 board to one of the four other options, with 9x9 being the hardest.
Overall, we enjoyed playing Flow Free. It was easy to learn, and there were enough options to keep the game interesting in replay. The one downside is that the free version is supported by advertising. If you want to skip the ads, you'll have to pay, but that will also net you another 150 levels, which might be worth the upgrade.