Players move alternately, starting from the player having Black stones.
Each move consists of one or two steps: placing a stone and claiming a rectangular region of tiles.
The first step (placing a stone) is mandatory. A stone can be placed on any unoccupied intersection meeting the following conditions:
 There should be at least one adjacent tile that is not claimed yet.
 Playing on the intersection should not cause the repetition of the same type of mirror move that was made by the player on his previous turn.



A stone can be placed on the specified intersections because there is at least one unclaimed tile (not highlighted squares) adjacent to each of them. 

A stone cannot be placed on the specified intersections because there are no unclaimed tiles adjacent to them. 
The second step (claiming a rectangular region of tiles) is optional, i.e. if some region can be claimed then a player can decide whether to do it or not. A rectangular region can be claimed if it meets all of the following conditions:
 There are four stones of the player's color placed on the four intersections forming the four vertices of the orthogonal rectangular region.
 There are no stones of either color in its edges or interior.
 There are no claimed tiles of either color in its interior.
Below are several examples of the rectangle regions, which are not eligible to be claimed by a player for some reason:





The highlighted rectangle cannot be claimed by the Black player because there are not four of his stones forming the vertices of the rectangle. 

The highlighted rectangle cannot be claimed by the Black player because there is a stone on its edge (D13). 

The highlighted rectangle cannot be claimed by the Black player because there are claimed tiles (two white tiles) in its interior. 
If all the conditions mentioned above are met and the player decides to claim the rectangle, then the player's four stones on the vertices of the rectangle are removed from the board and all the interior tiles of the rectangle are marked with the player's color:



The highlighted rectangle can be claimed by the Black player. 

The rectangle is claimed by the Black player and the four stones forming the vertices of the rectangle are removed from the board. 
