Kepler & K2 provide long-baseline, high-precision photometry for exoplanet and astrophysics research.
The basic and most common additional rule for Doubles play is that where a Double exists at the end of any train, the Double must then be 'satisfied' (laid against) in the next turn, even if the Double is on another player's train that is not marked.
The rules of Othello are much simpler than many other board games. However, easy to learn doesn't mean easy to play well. That comes from a good saying, 'one minute to learn, but a lifetime to master'! Each Othello checker is black on one side and white on the other. Black plays first and places a checker, black side uppermost, on any square on the board such that he 'sandwiches' at least one of his opponents pieces between the checker he has just placed and any other of his colour already on the board.