English-language Scrabble at club level in the UK. Tournaments follow a similar structure to American ones, usually at least 6 games but weekend tournaments where players play 12 to 16 games are not uncommon. The official Scrabble association the Association of British Scrabble players sanctions official tournaments with official ratings, ratings range from about 200 to about 60. The official dictionary is called SOWPODS. In contrast to American tournaments, players do not lose a move if they challenge a valid word, which in general means more words are challenged. There are only Scrabble competitions for primary and secondary school students in Hong
Latin square square is NP-complete. The popular Sudoku puzzles are a special case of Latin squares; any solution to a Sudoku puzzle is a Latin square. Sudoku imposes the additional restriction that nine particular 3×3 adjacent subsquares must also contain the digits 1–9 (in the standard version). The more recent KenKen puzzles are also examples of Latin squares. Latin squares have been used as the basis for several board games, notably the popular abstract strategy game Kamisado. Latin squares are used in the design of agronomic research experiments to minimise experimental errors. The Latin square also figures in the arms of the