This game is great - really like the aesthetic, the gameplay is challenging and (as cyrus mentioned), the AI seems really well done and fair. I could seriously see this being ported to a mobile device fairly easily, since having selection / movement as touch might even make it more intuitive and avoid the confusion with movement direction. A couple things I felt were missing might be a level select screen - I'm not great at these types of games and being able to go back and pick up where I left off would have been appreciated. Also, the tutorial didn't explain the selection process / controls exactly, so it took me a minute to figure out how to select (I was originally trying to select with the mouse. Doh!).
All in all, great job!