My wife and I finally bought Pentago:

This game is incredible. It’s won a few Game of the Year awards and it was one of  Mensa’s mind games in 2006. The rules are very simple: Get five in a row. After each move, you must rotate one quadrant of the board 90°. The rules are simple but the strategy is deep.

I first played it two years ago and have been meaning to get the game ever since. We finally got it last weekend and I’ve played it with as many people as possible since then. The photos above show my friend Brian’s favorite winning position (details of this strategy here). But there are lots of nice ways of winning–four to be exact. The aforementioned winning position, “The triple power play,”  is described as the most powerful winning position by this strategy guide (you were right, Brian!).

You can play online here. I tried it and beat the computer player pretty easily. See if you can do the same!