Your goal is to reach enemy ground. You are moving by drawing a line. You can move only by one square (vertical, horizontal, diagonal moves are allowed). You can't draw new line on existing line. If you end your move on point where another line ends, or a few other lines has a joint, you are able to perform another move. In this way you can do many moves in one turn, it's even possible to go cross all map by doing one huge combo.
There are 5 modes of game depending on intelligence of your computer opponent.