Oasis
Just installed a new game last night, and I have to say I'm enjoying it immensely. It's called Oasis, and it's a simple yet complex strategy game of founding a kingdom, building its defenses and defending it from the attacking barbarian hordes. The genius of the game is that it takes about 5 minutes to play a round. PC only, I'm afraid, but if you have one of those you should download the demo. It's basically a timed demo. You get an hour or so to try it out, after which you need to pay and download a key to keep going. After trying the demo, I couldn't resist paying for it immediately. The gameplay is perfectly designed, very easy to get into and understand yet, as you advance through the game and the difficulty increases, the thought you need to put into every move is really quite impressive. Give it a try.