# In reversi, can you overwrite two chips in one move?

In Reversi if you have a line of chips `--xxxy--`, you can place another `x` in the 5th position and overwrite the `y` you for sure can get the line `--xxxxx-` (where x is light, y is dark, and - is empty, line may be horizontal, vertical or main diagonal).

Can you do the same if the line contains one (or more) enemy chip in between? If you for example have `-xxyxyx-`, can you get `-xxxxxxx`?

No. From the Rules of Play:

1. Each piece played must be laid adjacent to an opponent's piece

2. so that the opponent's piece or a row of opponent's pieces is flanked by the new piece and another piece of the player's colour.

3. All of the opponent's pieces between these two pieces are 'captured' and turned over to match the player's colour.

where I have split up and numbered the clauses of the paragraph for easier reference.

Note that:

• from (1), the suggested move is illegal, not being adjacent to an opposing piece;

• even if one is playing to make `-xxyxy--` into `-xxyxyx-`, by (3) only the second 'y' is flipped, resulting in `-xxyxxx-` upon completion of the move; and

• playing to make `-xxxyy--` into `-xxxyyx-` does convert multiple opposing counters, by (2) and (3), flipping to yield `-xxxxxx-` upon completion of the move.

Reason:

"All of the opponent's pieces between the these two pieces [(the just placed piece and the enabling friendly piece at the far end of the just surrounded enemy row of pieces)] are 'captured' and turned over to match the player's colour."

• What about a case like `XYY-YYX` where an X is played in the center? Ignoring for the moment whether such a board scenario is possible, I would think that it would flip all the Ys as two separate lines can be drawn from the move coordinate: one to the left and one to the right. If not, what is the precedence when this is generalized to 2 dimensions? Say you have a move that would draw a line up and down-right, for example. Dec 31, 2021 at 20:47
• My expectation was correct Jan 1, 2022 at 7:00