Again, a non-free game and this one probably won't be in everybody's interest here, but what the heck. Frozen Synapse is a tactical simulation. It has very Tron-like graphics, and you control a squad of good guys against any number of bad guys inside a randomly generated building. Each type of unit has different attributes (range, speed, engagement speed, etc) and you spend as long as you want planning out what you are going to do for the next 5 secs (and replaying that as many times as you want until you commit to a move). The trick is, the opponent is doing the same thing, trying to guess what you are doing while you are trying to guess what they are going to do while countering them. Then the computer calculates what happened by moving both sides simultaneously. There are some crazy options for multiplayer, like play-by-email and the like that haven't been around very much lately.

It can be pretty questionable, the second mission in the single player campaign has you against a group of unarmed researchers. Like I said, not for everybody.