Cross-codes is making a crossword puzzle, but with codes.
For example, We have a 10*10 (not constant, this means the size may vary for each contest) grid:
..........
..........
..........
..........
..........
..........
..........
..........
..........
..........
And your code is MY_CODE
, you can place your code anywhere in the grid, vertically or horizontally.
For example:
..........
...MY_CODE
..........
..........
..........
..........
..........
..........
..........
..........
Next, Let's assume the next code is MOM
.
The poster could place it like
..........
...MY_CODE
...O......
...M......
..........
..........
..........
..........
..........
..........
But not like:
..........
..MMY_CODE
..O.......
..M.......
..........
..........
..........
..........
..........
..........
Because it is adjacent to another code which is MY_CODE
, making it look like MMY_CODE
.
The winner would be the one with the most codes placed, when there is nobody able to place a new code on the grid for a set time period (ex.1 week).