Like any good infection, your goal in Pathogen is simply to spread as far as possible. The game, which is available now on iPhone and iPad, is essentially a beefed-up version of Reversi: you place nodes on the screen, and by placing them near your opponents' nodes you can take over their territory. Whoever has the most territory when there aren't any moves left wins. What makes Pathogen different is that there's a hierarchy to the nodes, and lower level ones can't be used to take over those of a higher level. There are only three levels to deal with, but they add enough complexity to make Pathogen a satisfyingly addictive strategy game that doesn't ease up on the difficulty.

What makes the game particularly challenging is that the higher-level nodes take time to recharge before you can use them, so you'll need to be very careful about when and where you use them. You really need to think a few moves ahead: it's possible to set up chain reactions that undo much of your opponent's hard work with a single move (and that's not even mentioning the virus option, which simply wipes out a huge chunk of adjacent nodes). The single-player campaign features plenty of levels to play through, each with different layouts and difficulty levels, and there's also a multiplayer mode (both local and online) in case you manage to get through all of the missions.

Pathogen's simple-yet-addictive gameplay is augmented by a terrific presentation, with visuals that make it feel like you're playing on a computer from a 1980s sci-fi film. It also has a great electronic soundtrack that just begs for a good pair of headphones, and when you place a node you'll hear a satisfying piano clink. You can grab it now for $2.99 at the source link below.