The potential scope for games and apps is rapidly increasing, but sometimes the simple things are still the most effective. Flow Free is a puzzle app that takes a basic idea and makes a satisfying and challenging game out of it.

You're given several coloured pairs of dots on a grid. You have to draw a line to connect each pair without any of the lines crossing over. It's a very simple premise, but one that offers plenty of variation (the app boasts over 1,000 puzzles).

The game starts you off with a 5x5 square board and just four colours, but as you progress you're confronted with larger boards and more pairs to connect. At the hard levels you can have nine different colours to connect on a 9x9 board, and this can be a real challenge. There's something quite satisfying about connecting up the last two dots and seeing the whole screen covered with your lines (which the game unaccountably refers to as pipes, although I'm sure they have their reasons). If you get to the point where you start to feel like you've mastered Flow Free there's also a time trial mode to give the game an extra level of difficulty.

Each round of Flow Free is usually quite brief, and this is to the game's advantage – if you want to sit down and have a lengthy spell with it you can, but if you just want a quick distraction while you wait for your bus to arrive or your coffee to brew then one or two levels is a great time-filler.

While the presentation is fairly basic it's bright and colourful, and very easy to follow. For a game like this you wouldn't want too much clutter as it would just get in the way. There are ads on the bottom of the screen and occasionally one will pop up after you finish a round, but they're not so obtrusive as to be annoying.

Flow Free is a game that doesn't try to do too much, and so succeeds well at what it does. If you enjoy visual puzzles like Tetris or the like then you could do a lot worse than Flow Free for an enjoyable take on the genre.