Frozen Synapse triggers the same tactical parts of the brain as Chess. You have to see your moves and your enemy's moves well in advance. Then, take into account weapon type, enemy focus, and missions and you have yourself a game well worth the price. Beyond that, the base game comes with two copies -- one for you and one for a friend. Combine that with the DLC (or get the complete pack) and you and a buddy have a solid weekend of entertainment with more down the line.

I do want to note, however, that online play often suffers during times of Steam sales because the servers just can't handle the new traffic. Luckily, you can still play offline. The traffic issue sorts itself out in a day or two.