A Summary of the Rules.

This is chess played on a Go board.
The difference is that you aren't stuck with the original pieces -- a piece is what you make it, by selecting any 3 by 3 set of squares. Its power depends on the configuration of stones in it -- a powerful piece has lots of stones, especially a center one.
A piece can only move in the direction that has a square on its outside edge. If you look at the initial setup, you'll see Rooks in the corner squares, as in chess. These pieces have empty corner squares, so they can't move diagonally. But they do have stones in the middle of each side, so can move from side to side and backwards and forwards.
Where Gess is different is that you can select a piece that's half Rook and half Bishop.
If you click on d3 you'll be able to move like a Rook and a Bishop to the left, but only like a Bishop to the right.
A Piece moves 3 squares if its center is empty, as far as possible if its center is full.
A Ring, corresponding to the King in chess, is 8 stones around an empty center. You start with one Ring, but you can, theoretically, make another by moving pieces together. You lose if your last Ring is broken.