Othello Rules

1. Starting Position
An Othello game always starts off with this position shown below with two discs of each colour intersecting each other diagonally. The top right disc is always the black one from either players' view sitting opposite each other.

2. Making a Move
Black always makes the first move.

In order to make a legal move, one must first place a disc of his or her colour on one of the empty squares on the board. The disc that is being placed on the board must directly sandwich one or more of the opposing colour's disc(s) in horizontal, vertical or diagonal directions with one or more of the existing disc(s) on the board. This action is followed by flipping all sandwiched disc(s) on the board in the appropriate direction.

For example, if Black makes a move to F5, he must flip the white disc on E5 as shown on the right:

The end result after F5 is played is shown in the diagram on the right:

Thus, in the starting position, Black essentially has 4 possible legal moves as marked by the red crosses to C4, D3, E6 and F5 on the right:

By playing C4 or D3, Black will be able to flip the white colour D4 disc in the horizontal or vertical directions respectively.

By playing F5 or E6, Black will be able to flip the white colour E5 disc in the horizontal or vertical directions respectively.

The game continues with White making the next move in the same manner by playing a disc on one square of the board which one or more black disc(s) may be flipped in the horizontal, vertical or diagonal directions.

Thus, after F5 is played, White has essentially 3 possible choices   as marked by the red crosses to D6, F4 or F6 on the right:

By playing D6, F4 or F6 to the board on the right, White will be able to flip the black colour E5 disc in the vertical, horizontal or diagonal directions respectively.

3. Completing the move
In order to complete a move, all of the disc(s) that are possible to be flipped must be flipped.

For example, in this case, when black disc G8 is played, Black will have to flip 6 white discs in the horizontal, vertical and diagonal directions which is a total of 18 discs.

Another example, a more exaggerated one would be as follows. when black disc D4 is played, Black will have to flip multiple discs in a total of 8 different directions. This move garners a total of 19 discs in one single move which is the maximum number of discs one could flip in one move.

The same effect is possible when moving to D5, E4, or E5 under similar situation. However, this example is merely hypothetical because the starting position already has these 4 squares filled up!

Therefore, the most number of discs you could possibly flip in a real game is still 18 discs in one move as shown in the example above.

4. Game Progression
Both players will continue to take turns and make their moves as the game progresses. In the event where one of the players has no legal moves (i.e. no discs to place on the board which can sandwich and flip at least one or more disc(s) of your opponent), he will have to make a PASS, and the other player will continue to play. In this example, since White has no legal moves, Black will get to play the last move on the A1 square to end the game.
After the move A1 has been played, White will have no legal moves. Black will also have no more legal moves (obviously because there are no more empty squares left on the board to play). The game will end when both players have no more legal moves and two consecutive passes have been made. However, if there is a legal move that either player may play on the board, it must be sounded off and played.

The final score will then be counted based on the number of discs on the board. The colour/side which has the highest number wins the game!

5. Final Scoring
There are times when both players have no more legal moves on the board while still having one or more existing empty square(s) on the board. In such cases, the empty square(s) will be counted and awarded to the side with more current discs of his or her colour on the board.

For instance, in this example shown, there are 32 black discs and 31 white discs. Black has more discs than White does and hence claims the empty square to his total score. The final score of this game would therefore, be 33-31 with Black winning the game. Basically, the score of both players in the final score reported should always add up to 64 irregardless of the shape on the board.

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